Four electric potential-pH diagramS for the sulfide-acid suspension systems of (H2S-H+, ZnS-H2SO4, CuS-H2SO4, PbS-HCl system) weredetermined at 97°C.
The potential (Esce) was measured by a Pt electrode VS. a saturated calomel electrode at that temperature and the intact values of the potential were used, The pH value was measured at room temperature.
For H2S-H+ (H2SO4 or HCl) system, two potentials were found at the fixed pH values, One by a fixed Pt electrode agree to the theoretical potential corresponding to the reaction.
H2S=2H++S°+2e
The other by a ratating Pt electrode is explained assuming the presence of S2 as follows
H2S=2H++1/2 S2+e
In the following stage the species S2may be oxidized to S°.
ZnS-H2SO4 system belonged to thelatter case as represented by
ZnS=Zn+++1/2 S2+e
whereas CuS-H2SO4 and PbS-HCl systems the former case as represented by
MS=M+1+S°+2e M: Cu++ or Pb++
