THE EFFECT OF HIGH-SPEED STIRRING ON THE DISTRIBUTION EQUILIBRIA OF NEUTRAL METAL-CHELATES

When a two-phase system comprising an organic solution of any of vario us interfacially active neutral metal chelates in contact with an appr opriate buffered aqueous phase is vigorously agitated, a reversible de crease in the organic phase concentration of the chelate is observed. This decrease gives rise to a shift in the pH(1/2) value of the metal ion (i.e., the pH corresponding to 50% extraction) from that observed in the corresponding unstirred system. The magnitude of this shift is shown to vary with the distribution constant of the chelate, the inter facial area generated upon stirring, and the organic solvent. In syste ms in which a pair of extractable metal chelates differing in interfac ial activity is present, the shifts in pH(1/2) are shown to alter the apparent selectivity of the chelating extractant and to enhance the se paration of the metal ions.