Catalytic polarographic waves of cobalt(II) in the presence of sodium sulfide (SH− form) in borax – ammonium chloride

Abstract

The presence of SH− ions in a medium containing ammonia (borax–NH4Cl) and cobalt(II) gives rise to a catalytic cobalt(II) prewave and a catalytic hydrogen wave, both of which manifest more positive potentials than the cobalt(II) reduction wave. The effects of time, sulfide and cobalt concentrations, mercury column height, and gelatine and neutral salts addition are discussed. In addition, the characteristics of the current–time and electrocapillary curves are shown. The results obtained suggest a mechanism whereby a cobalt(II) prewave is produced by a cobalt(II) complex with SH− in the 1:2 relationship. Hydrogen catalytic evolution is attributed to the reduction of a protonated complex.