Extraction of calcium by a nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5

Extraction of calcium by a nitrobenzene solution of bis-1,2-dicarbollylcoba ltate in the presence of 15-crown-5 (15C5, L) has been investigated. The eq uilibrium data and the typical maxima concerning the dependence of the Ca d istribution ratios on the analytical concentration of 15C5 in the system un der study can be explained assuming that the HL+, HL2+ and CaL2+, CaL22+ pa rticles are extracted into the nitrobenzene phase. The values of the corres ponding extraction and stability constants of the extracted species in nitr obenzene saturated with water have been determined and the mutual Sr/Ca sep aration has been discussed.