Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of N,N,N′,N′-tetraethyl-2,6-dipicolinamide (TEtDPA, L) has been investigated. The equilibrium data have
been explained assuming that the cations HL+, HL23+, ML23+ and ML33+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. It has been found that the stability constants of the corresponding complexes EuLn,org3+ and AmLn,org3+, where n = 2, 3 and L is TEtDPA, in the mentioned medium are comparable.