What does a distribution coefficient show in liquid-liquid extraction?

In liquid-liquid extraction, the distribution coefficient represents the ratio of a substance's concentrations or solubilities when it is distributed between two immiscible liquids at equilibrium.12

This value is a characteristic property of a specific compound paired with a particular set of solvents. Because substances with different molecular structures typically exhibit widely different distribution coefficients, chemists use this ratio to determine the feasibility of separating mixtures. Compounds with highly similar coefficients, such as certain proteins, require more complex, multistage processes like countercurrent distribution to achieve effective separation.1