Anion complexer strength

Azuma and Kametani also explored the effect of anion complexer strength. A direct relation between stability constant of the Fe +Zanion complex and dissolution rate was found. Of all the acids examined, HF, which forms the most stable Fe complex, was found to be the most vigorous solvent. Gorichev et al. ° also investigated the effect of the anion of the acid. They found that data for all of the acids at various concentrations could be represented as one plot of a vs. t/to.s, where to.s is the half-life of the oxide. This has been interpreted to mean that the rate-determining step is the product of two independent functions and may represent the same mechanism for all of the acids. Thus, the rate coefficient of Equation (16) may be expressed by... 

Complex Cation bonding strength (vu) Anion bonding strength (vu) ... 

The extent of speciation in solution depends on the stoichiometric coefficients of the components of a species the polyvalent nature and protonation behaviour of anionic complexing ligands the type and relative ability of different cations and anions to form complexes pH ionic strength, and the ratio of the total concentrations of the reactants in solution (the total cation anion ratio). 

One must conclude as for the monovalent counterion sequences referred to in the Introduction that interaction between bivalent cations and anions is a complex phenomenon not determined solely by simple electrostatic considerations and ion size. Of the current hypotheses that explain ion sequences, that of Eisenman (45), based on anion field strength and recently expanded to include divalent cation effects (46, 47), seems the most comprehensive. However, we believe a fundamental understanding of these systems awaits better knowledge of the role of such factors as water structure, hydration, and geometric effects, including orientation associated with the presence of an alkyl group and of pH. Studies on a more extensive range of cations are required for all the cited systems, with the possible exception of those based on fatty acids. 

The extraction behavior of No + in a tri-n-octylamine-HCl system was compared with that of divalent Hg, Cd, Cu, Co, and Ba (27). This experiment provided a test of the chloride complex strength of No2+ because the amine anion-exchanger will only extract anionic species. It was found that Ba + and No + were not extractable over a range of 0.2 to 10 M HC1, while the other divalent ions of Hg, Cd, Cu, and Co were strongly extracted. 

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