Solvent extraction.Distribution coefficient and its Limitations.

 Solvent extraction.

Distribution coefficient and it's Limitations. 



Distribution coefficient:


According to Nerst Distribution law, 

"When solute distributes itself between the two immiscible solvents or phases in contact and in equilibrium with each other, then the ratio of the concentrations of the substance in the two phases is constant at constant temperature. "



Thus, 

S1/S2=kD

Where,

 kD -is distribution constant or partition constant. 

S1- is Concentrations of the solute in mols/ litre in organic phase ( phase 1) . 

S2-is Concentrations of the solute in moles / litre in aqueous phase ( phase 2) 

kD -is the independent of the total solute or either of the phases. 

This law takes no account of the activities of various species. 

Therefore it is applicable only for dilute solutions. 


Limitations of Distribution Law. 


1.The Solution must be dilute. 

2.The temperature remains constant. 

3.The two solvents are immiscible. 

4.The molecular state of the solute remains the same in the two solvents. That means the solute does not undergo association, dissociation, Polymerization or interact with other dissolved species. 















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