Extraction of calcium and strontium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of 1,2-(diphenylphosphino)ethylene dioxide

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of 1,2-(diphenylphosphino)ethylene dioxide (DPPEDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL+, HL2+, CaL22+, CaL32+, CaL42+, SrL22+ and SrL32+ are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability constants of the CaLn2+ complexes, where n = 2, 3 and L is DPPEDO, are somewhat higher than those of the corresponding complex species SrLn2+. (author)