Estimation of Stability and Solubility Constants

The reaction of a metal ion, M, with a hydroxide ion to produce the species has been described by reaction (2.5). The stability constant for this species is shown in Eq. (2.6). Brown, Sylva and Ellis (1985) demonstrated that the stability constant, could be predicted from chemical and physical properties of the reacting metal ion. The stability constant could be described by Eq. (2.92)  

In these equations, S depends on the presence (S = 1) or absence (S = 0) of s-electrons in the outermost shell of the ion (i.e. those metal ions exhibiting 

Solid-state measurements have shown that the ionic radius of oxo-cations such as dioxouranium(VI) is a function of both the nature and number of ligands bonded to the central metal ion (Zachariasen, 1954). Subsequently, it was shown that a similar dependence occurs in aqueous solution (Brown and Sylva, 1987). This latter study demonstrated that the value of the function g izlr +g2) was dependent on the nature of the binding ligand, specifically its dissociation constant, where r in the function could be replaced by r (i.e. the function 

Baes and Mesmer (1976) examined the relationship between the solubility of a hydroxide or oxide phase and the formation of the first monomeric hydrolysis species. For the reaction 

Baes and Mesmer found that the latter expression could be approximated by a constant, that is. 

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