Table 2: Negative logarithms of the acidity constants of DPA and logarithms of the stability constants of the corresponding binary Co-DAP complexes in dependence on the amount of dioxane added to water at I = 0.1 mol dm−3 (NaCl) and 25 °C.
| % (v/v) Dioxane | pK1 | pK2 | Sc | ||
| DPA | |||||
| 12.5% | 7.85(0.03) | 10.42(0.02) | 2.91E−6 | ||
| 25% | 7.98(0.03) | 10.62(0.01) | 5.91E−6 | ||
| 37.5% | 8.12(0.01) | 10.81(0.02) | 2.91E−6 | ||
| 50% | 8.34(0.03) | 10.92(0.02) | 4.50E−6 | ||
| 62.5% | 8.53(0.03) | 11.22(0.05) | 5.71E−7 | ||
| Co-DPA | |||||
| 12.5% | 4.75(0.02) | 7.15(0.02) | 7.67E−7 | ||
| 25% | 4.95(0.04) | 7.45(0.04) | 5.35E−6 | ||
| 37.5% | 5.17(0.03) | 7.83(0.02) | 4.71E−7 | ||
| 50% | 5.54(0.01) | 8.15(0.03) | 5.91E−6 | ||
| 62.5% | 5.96(0.03) | 8.46(0.04) | 6.74E−7 | ||
| cSum of square of residuals. | |||||