We hypothesize that this reaction could represent disproportionation
of slower reacting polysulfides (to liberate sulfide and
TNB eventually), which only start operating when TNB-persulfide
is consumed. Consistent with this assumption the rate of this reaction
was independent of the sulfide concentration, but a more
detailed investigation of this minor reaction is outside the scope
of the present study. The stoichiometric ratios in Table 1 include the
absorbance changes of this step.