Extraction of Co(II) complexes of nine 1-alkylimidazoles (with R = C4H9 to C14H29) from aqueous solution (I = 0.5, KNO3, at 25degreesC) with toluene, omicron-xylene, dichloromethane, and 2-ethyl-1-hexanol was studied. Stability constants of the complexes formed in the aqueous phase and partition constants of the extracted species were determined. Both the stability constants (beta(n)) and partition constants (P-11) of the complexes increase with increasing length of the alkyl chain. The more soluble 1-alkylimidazoles was found to form tetrahedral and octahedral Complexes at the third and fourth step of complexation. The appearance of the octahedron reversible arrow tetrahedron configuration equilibrium was found to depend on the nature of the solvent used.