Optionally substituted benzimidazoles containing an alkyl or cycloalkyl group in position 1 and containing at least 5 alkyl or cycloalkyl carbon atoms extract metals from aqueous solutions of their salts into water-immiscible organic solvents in presence of halide ion. Benzimidazoles having a branched-chain alkyl group of at least 7 carbon atoms in position 1, and especially mixtures of such compounds, are most effective. The benzimidazoles are particularly useful for extracting cobalt selectively from mixtures of cobalt and nickel salts. The metals can be recovered from the organic solvent by extraction into water free from halide ion.