Solvent extraction of sodium perrhenate by 3m-crown-m ethers (m=5, 6) and their mono-benzo-derivatives into 1,2-dichloroethane: Elucidation of an overall extraction equilibrium based on component equilibria containing an ion-pair formation in water.

Equilibrium constants (K(MLA)(0)/mol(-1)dm(3)) for the ion-pair formation of a complex ion NaL(+) with ReO(4)(-) in water were determined potentiometrically at 25 degrees C and the ionic strength (I) of 0mol dm(-3) using a Na(+)-selective electrode. Here, crown ethers, L, were 15-crown-5 ether (15C5), benzo-15C5, 18-crown-6 ether (18C6) and benzo-18C6. Also, NaReO(4) was extracted by the L into 1,2-dichloroethane and then extraction constants (K(ex)/mol(-2)dm(6)) for the species, NaLReO(4), were determined at 25 degrees C by AAS. These K(ex) values were resolved into four component equilibrium constants containing K(MLA) calculated at given I values. Based on these data, extraction-abilities of the L against the perrhenate were discussed in comparison with those of sodium picrate-L systems reported previously.