Stepwise Stability Constants, K and

The numerous Cd-PC2 species that exist in aqueous solution require specialized software for complete stability constant analysis. The basic principles behind the calculation, however, are well pointed out by considering a very simple reaction between the already doubly deprotonated amino acid, A-, and Cd2+ aqueous ion, equations (7.10)-(7.11). [Note this holds strictly only for glycine. In the cysteine system, the N-terminus is protonated (Cys should really be represented as HA).] 

Again free [A ] and [HA] need to be put into terms that we can measure or that are known. Under our given assumptions, they become  

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Fig. 11.50 Stepwise stability constants. K. and Kj, for ethylenediamine complexes of several first-row transition metals in aqueous solution.

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