The mechanism of the 2nd step of electroredn. of S in DMSO was studied by electrochem. methods. The reduction process appears as a simple electron transfer reaction when the scan rate is >200 mV/s and becomes complicated by coupled homogeneous reactions (ECE mechanism) when the scan rate is <200 mV/s. Sep. anodic peaks for S84-, S32- and S42- were discovered at potentials of -1.50, -0.96 and -0.60V, resp. (vs. a Ag ref. electrode). The formal standard potential and standard rate constant for the S82-/S84- couple were calculated to be -1.547 ?0.002V vs. a Ag. ref. electrode and 3.3 ?10-3 cm/s, resp.

Key words: SULFUR, OXIDATION REDUCTION REACTION, PROTONS, MEDIA, MECHANISM, MERCAPTO GROUP, DMSO, ELECTROCHEMICAL REACTION