Evaluation of overall extraction constants for the crown ether-complex ions of alkali and alkaline-earth metal with counter picrate ions from water into nitrobenzene based on their component equilibrium constants

► Extraction constants into nitrobenzene for 28 crown ether-complexes are evaluated. ► An effect of dehydration of these complex ions on the constants is discussed. ► Separation of Ba2 + from Sr2 + or Ca2 + by the ethers is predicted from the constants.