Table 2.
Experimental stability constants 1 of Fe3+/(3,4-HP) species obtained by different analytical techniques at I = 0.15 mol L−1 in NaCl(aq), different temperatures and p = 0.1 MPa.
| logβpqr (logKpqr) | ||||
|---|---|---|---|---|
| T = 298.15 K | T = 310.15 K | |||
| Species | Potentiometry | UV–Vis Spectrophotometry |
Average Stability Constants 2 |
UV–Vis Spectrophotometry |
| FeH(L1)2+ | 17.37 ± 0.10 3(7.42) | - | - | - |
| Fe(L1)+ | 13.23 ± 0.19 | - | - | - |
| Fe(L1)2- | 22.52 ± 0.20 (9.29) | - | - | - |
| FeH(L2)2+ | 26.16 ± 0.03 3(15.43) | 25.91 ± 0.043(15.18) | 26.03 ± 0.10 4(15.30) | 26.23 ± 0.01 3(15.24) |
| Fe(L2)+ | 22.06 ± 0.06 | 21.78 ± 0.03 | 21.97 ± 0.11 | 22.86 ± 0.04 |
| Fe(L2)2- | 38.01 ± 0.04 (15.95) | 38.01 5 (16.23) | 38.01 ± 0.11(16.04) | 39.79 ± 0.08 (16.83) |
| FeH(L4)2+ | 26.31 ± 0.02 3(15.21) | - | - | - |
| Fe(L4)+ | 22.48 ± 0.03 | - | - | - |
| Fe(L4)2- | 39.08±0.03 (16.60) | - | - | - |
| FeH(L5)3+ | 25.05 ± 0.04 3(13.97) | 24.85 ± 0.04 3(13.77) | 24.95±0.15 4 (13.87) | 25.35 ± 0.04 3(14.75) |
| Fe(L5)2+ | 20.93 ± 0.03 | 20.30 ± 0.03 | 20.61±0.27 | 21.16 ± 0.08 |
1 logβpqr and logKpqr refer to Equations (2) and (1), respectively; 2 values obtained by an average of potentiometric and UV–Vis spectrophotometric data; 3 ±Std. Dev.; 4 errors on weighed data; 5 value kept constant from potentiometric data. Standard uncertainties: u(T) = 0.1 K; u(I) = 0.01 mol L−1.