\(\mathrm{E}^{0}_{\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}}=+0.77 \,\mathrm{V}\)
\(\mathrm{E}^{0}_{\mathrm{Co}^{3+} / \mathrm{Co}^{2+}}=+1.97\, \mathrm{V}\)
\(E^{0}_{\mathrm{Mn}^{3+} / \mathrm{Mn}^{2+}}=+1.57\, \mathrm{V}\)
$FeCr _{2} O _{4}+ Na _{2} CO _{3}+ O _{2} \rightarrow A + Fe _{2} O _{3}+ CO _{2}$
$A + H ^{+} \rightarrow B + H _{2} O + Na ^{+}$