Characteristics of Diluents:

After having seen the various roles of diluents, it may be easy to define their essential characteristics which are listed below:

i) It should be mutually soluble with an extractant or modifier.

ii) It should have high solvency for the extracted metal species; thus, providing a high metal loading capacity to the solvent and minimizing the problem of third phase formation.

iii) It should have low volatility and a high flash point. This minimizes the losses due to volatility and fire hazards.

iv) It should be in its own right insoluble in the aqueous phase.

v) It should have low surface tension.

vi) It should be cheap and readily available in large quantities.

The choice of diluents ranges from simple molecules to complex mixtures.

They are both aliphatic and aromatic. The simple molecules that are routinely used at the laboratory scale are n-hexane, cyclohexane, benzene, toluene, xylene, chloroform, carbon tetrachloride and chlorobenzene. The use of some of these is restricted due to environmental or toxicological considerations. The cost can also be a deterrent.