Solvent extraction of strontium and barium into nitrobenzene by using synergistic mixture of hydrogen dicarbollylcobaltate and dibenzo-24-crown-8

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H(+)B(-)) in the presence of dibenzo-24-crown-8 (DB24C8, L) has been investigated. The equilibrium data have been explained assuming that the species HL(+), HL(2) (+), ML(2+), ML(2) (2+) and MHL(2) (3+) (M(2+) = Sr(2+), Ba(2+)) are extracted into the organic phase. The values of extraction and stability constants of the complexes in nitrobenzene saturated with water have been determined. It was found that the stability constants of the cationic complex species BaL(2+) and BaL(2) (2+) in the considered nitrobenzene medium are somewhat higher than those of the corresponding complexes SrL(2+) and SrL(2) (2+).