A preliminary study was devoted to the Fe(III)/Fe(II) redox system.
Solutions containing various proportions of Fe(II) and Fe(III)
sulphates were prepared. The activities of Fe2 aq and Fe3
aq in these solutions were computed using the MINTEQA2 software [31]. The
various Fe(II) and Fe(III) complexes likely to form in the solutions
(FeSO0 4, FeSOþ 4 , FeOH2+, FeðOHÞ þ 2 ) were all taken into account. The
corresponding data are given in Tables 1 and 2. The equilibrium
pH of the solutions was also computed and found close to the measured
values given in Table 1. Of course, the computed activity values
of Fe2 aq and Fe3 aq take the variations of pH into account.