Abstract: Extraction of alkali metal picrates with Schiff base and secondary amine type bis-crown ethers containing benzo l5-crown-5 moiety was carried out in the medium of chloroform as water immiscible solvent. The compositions of the complexes were determined indirectly by measuring the conductance of acetone solutions of alkali metal tetraphenyl borate-crown ether. It showed that these bis-crown ethers probably formed 2:1 complexes with K⁺, Rb⁺, Cs⁺. The distribution ratio,extraction equilibrium constants K_e were also measured. The K_e dataindicated that for the same alkali metal picrate, the Schiff-base type bis-crown ethers give smaller values than the secondary amines. The secondary amine typebis-crown ether F₂ exhibited the greatest effectiveness of extraction and selectivityfor potassium ions.

Key words: Schiff base type bis crown ether, Secondary amine type bis-crown ether, Extraction equilibrium constant, Conductometry