25.2.1—Terms: partition coefficient, Kpc

For a solute distributed between two immiscible solvents, Kpc = concentration in one named solvent divided by concentration in the other at equilibrium and fixed temperature.

State which solvent is numerator and keep phases/units consistent. Kpc describes equilibrium distribution, not the total amount extracted in one operation.

If Kpc(organic/aqueous)=4, the equilibrium concentration in the organic phase is four times that in the aqueous phase under the stated conditions.

Do not invert Kpc without changing the definition, and do not assume a large Kpc means one extraction removes all solute.