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How to Calculate the Coefficient of a Partition

The partition coefficient, or K, is measured most commonly for solvents such as ethanol, benzene, cyclohexane and isopropanol. It's a measure of the ratio of a solvent in the sample phase and the gas phase. Solvents that have a low K value will more readily go into the gas phase, while solvents with a high K value will stay in the sample phase. The measurement is most often taken in an air-water system held at a constant temperature and pressure.

Solvent reference materials

Instructions

- 1
  Find the concentration of the solvent in the sample phase. This variable is commonly denoted by "Cs" and will depend on the temperature of the system. Measurements can be found in solvent reference materials.
- 2
  Find the concentration of the solvent in the gas phase. This variable is commonly denoted by "Cg." Be sure to use the same temperature as in the previous step.
- 3
  Divide Cs by Cg. For example, if the Cs of ethanol at 40C is 2710 and the Cg at 40C is 2, then 2710/2 equals 1355. The resulting value is the partition coefficient.

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