Figure 3

Experimental Zn(II)–ligand conditional stability constants (logβ) for (a) citrate and (b) DFOB at 0.05, 0.15, 0.3, 0.5 and 1 mol dm⁻³ in NaCl solution (open circles) determined using potentiometric titrations. For each species, the Extended Debye-Hückel (EDH) model has been parameterised using the experimental data (see Table 1 for C and logβ⁰) and the corresponding model is shown as a solid line. Literature data is included in the figure for comparison (closed circles) from Cigala et al. (2015, NaNO₃ and NaCl), Capone et al. (1986, KNO₃), Daniele et al. (1988, KNO₃), Field et al. (1975, KNO₃), Matsushima et al. (1963, NaCl) and Li et al. 1959, NaCl) for the Zn–H–Cit system and from Schijf et al. (2015, NaClO₄), Farkas et al. (1997, KCl) and Hernlem et al. (1996, KNO₃) for the Zn-H-DFOB system. Note the large variability reported for the Zn–Cit system at 0.1 and 0.15 mol dm⁻³. We find good agreement with the data published by Sammartano and co-workers^26,69.