Quantitative treatment of solvent extraction equilibria

The solvent extraction of a neutral metal chelate complex formed from a chelating agent HR according to the equation 

The various equilibria involved in the solvent-extraction process are expressed in terms of the following thermodynamic constants  

The distribution ratio, i.e. the ratio of the amount of metal extracted as complex into the organic phase to that remaining in all forms in the aqueous phase, is given by 

The difference in pH 1/2 values of two metal ions in a specific system is a measure of the ease of separation of the two ions. If the pH1/2 values are sufficiently far 

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