Variables
Description
What is this formula?
The distribution coefficient quantifies how a solute partitions between two immiscible phases at equilibrium. It indicates the preference of a compound for one phase relative to the other.
When to use it
Use this formula when designing liquid-liquid extraction systems, solvent recovery processes, hydrometallurgical operations, or pharmaceutical separations.
Example
A solute reaches equilibrium between an organic solvent and an aqueous phase. The concentration in the extract phase is 2.4 mol/L, while the concentration in the raffinate phase is 0.6 mol/L.
Formula:
KD = Ce / Cr
Substitution:
KD = 2.4 / 0.6
Result:
KD = 4.0
The solute concentration in the extract phase is four times higher than in the raffinate phase.
Applications
- Liquid-liquid extraction
- Hydrometallurgy
- Solvent recovery
- Pharmaceutical purification
- Environmental remediation
Note
The distribution coefficient is generally not constant and may vary with temperature, concentration, pH, ionic strength, and solvent composition. Some systems may exhibit non-ideal behavior requiring activity coefficient corrections.