In the reaction FeC₂O₄ → Fe³⁺ + 2CO₂, the equivalent mass FeC₂O₄ is

$\stackrel{+2}{\mathrm{Fe}}\stackrel{+3}{{\mathrm{C}}_2}{\mathrm{O}}_4 \to {\mathrm{Fe}}^{+3}+ 2\stackrel{+4}{\mathrm{C}}{\mathrm{O}}_2$

n-factor=change in ox. state of Fe + change in ox. state of 'C'=1+2(1)=4

${\mathrm{E}}_{{\mathrm{FeC}}_2{\mathrm{O}}_4}=\frac{\mathrm{Mol}.\mathrm{wt}.}{3}$