Solvent extraction of some divalent metal cations into nitrobenzene by using a synergistic mixture of strontium dicarbollylcobaltate and nonactin

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M2+(aq) + 1 · Sr2+(nb) ↔ 1 · M2+(nb) + Sr2+(aq) taking place in the two-phase water-nitrobenzene system (M2+ Mg2+, Ca2+, Ba2+, Cu2+, Zn2+, Pb2+, Mn2+, Ni2+; 1 = nonactin; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1 · M2+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following order: Mg2+, Mn2+ < Ba2+, Cu2+, Zn2+, Ni2+ < Sr2+ < Ca2+ < Pb2+. (author)