Solvent extraction of ion pairs by polar solvents

A survey is given of the physical chemistry of extraction with dissociation in the organic phase. The use is explained of the ion exchange extraction constant and the affinity discussed of extracted particles to the organic phase, the effects of the solvent, the effects of the water dissolved in the organic phase, the effect of the ''inert'' diluent and the choice of the hydrophobic anion as an extractant for the extraction of cations. A brief description is given of the behaviour of certain extraction systems: the extraction with tris-pyrocatechine arsenic acid, polyhedral borates and in the presence of neutral cation carriers of the type of polyethylene glycols and crowns. (M.K.)