ION-PAIR EXTRACTION OF LANTHANOID(III) WITH CROWN ETHERS AND PICRATE ION

The extraction of lanthanoid(III) with 15-crown-5, 18-crown-6, or dibenzo-18-crown-6, and picrate ions into chloroform was measured at 25 degree C. The stoichiometry of the dominant species extracted was found to be 1:2:3 with respect to lanthanoid(III), crown ether, and picrate ions. The extraction constants decrease through the lanthanoid series (except lanthanum). The constants for praseodymium or neodymium are larger than that for ytterbium or lutetium by an order of magnitude. The present result suggests that lanthanoid(III) would not be trapped in the center of the cavity of the crown ether.