Figure 5.

Model function B fitting to the experimental results ($c=5·{10}^{-4}\mathrm{mol}·{\mathrm{L}}^{-1})$, where it is assumed that ${\mathrm{H}}_2{\mathrm{GA}}^{2-}$ protonation species reacts with Fe(II) ions to form the coordination compound ${[\mathrm{H}}_2\mathrm{GAFe}]$ ($R^2=0.994$).