Partition and distribution constants of alkali-metal (lithium, sodium, potassium, rubidium) picrates in the waterÈbenzonitrile solvent system and ion-pair formation constants for these electrolytes in the water saturated organic phase at 298.15 K derived from distribution data are reported. Partition data are discussed with respect to transfer data for these electrolytes referred to the process involving the pure solvents. The extraction of alkali-metal picrates from water to benzonitrile by ethyl p-tert-butylcalix(4) arene tetraethanoate is investigated taking into account the extent of ion-pair formation of the alkali-metal complex salt in benzonitrile. A quantitative assessment of the individual processes which contribute to the overall extraction of alkali-metal picrates by the calixarene ester from water to benzonitrile is reported for the Ðrst time.

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