Selectivity in Concentrated Solutions

Ion exchange between resins and concentrated external electrolytes is generally far more complex compared with the situation for dilute solution. The same general selectivity determining considerations apply, but deviations from behaviour described for dilute systems can be anticipated on the basis of  

Lower water activity in the solution phase may result in the full solvation requirements of ions not being met, thus changing the ion-ion and ion-solvent energetics described for dilute solutions thereby changing the relative affinities. 

Ligands such as ammonia, amines, and polyhydric alcohols may be exchanged between an external aqueous phase and resins carrying ions capable of forming coordination complexes, thus providing a powerful technique for studying complex ion structure and complex formation equilibria. 

A typical impurity of epttimercial concentrated liydroGhloric add is iron. This is present as an anionic complex FeGL—i This is removed on a strong base anion exchange resin in the chloride form Ad the complex only exists in 

Concentrated HCl in which iron is dissolved to giw a 0,005 M Fe solution NarroWglass column, -12 mm diameter (approx,) O  

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