EXTRACTION OF HCLO4 AND HREO4 BY DILUTE SOLUTIONS OF TRIBUTYL PHOSPHATE IN CARBON TETRACHLORIDE ISOOCTANE AND 1,2-DICHLOROETHANE

The extraction of HReO4 or HClO4 into dilute solutions of tributyl phosphate (TBP) in CCl4, isooctane, and 1,2-dichloroethane has been studied, and the extracting species have been determined. A previous study of TBP in CCl4, where the TBP concentrations were 0.03 to 0.3 M and the stoichiometric ratio TBP/H+ was > 3, indicated the only extracting species were the molecular adduct TBP·H2O and the hydronium ion species 3TBP·H3O+·pH2O ⋯ ClO4-, an ion pair, where 0 ≤ p ≤ 1.5. In this study even more dilute TBP solutions in CCl4 were examined, and a two-TBP acid complex, in addition to the three-TBP complex, was found. In the isooctane system either a two- or three-TBP acid complex, depending upon TBP concentration, was found to predominate. With 1,2-dichloroethane-TBP and at the organic-phase acid concentrations examined, only a dissociated three-TBP complex was found. In addition to an anion effect, it is suggested solvent effects upon both TBP and the extraction complex are changing, to a greater or lesser extent, the TBP coordination number of the extracted hydronium ion from three to two.