Distribution law

The Nernst Partition Law states the following:

When a substance A has the opportunity to not miscible with each other between two (eg, a gaseous and a liquid phase or two liquid phases) to distribute highly dilute phases physically:

Then this distribution leads such as in a chemical reaction to an equilibrium which is determined by the relationship

Is given, where K is the Nernst partition coefficient ( equilibrium constant ) and cA is the concentration of the substance in the respective phases. However, the activity would be to use instead of the concentration for concentrated solutions.

The physicist and chemist Walther Nernst presented on the distribution law in 1891. When extracting a substance due to the solubility of the immiscible phases results in a distribution. The Nernst Partition Law applies so if a substance A is present in a biphasic system in both phases in the same form, and the two phases are immiscible. The basis for the separation of mixtures by extraction that various substances between two phases distribute in different concentrations.

The distribution coefficient is usually given in tables for the system octanol / water. Was erected in the Nernst distribution law in 1891 by Walther Nernst, after which it is named. It has application in the extraction or where extraction of solutes from water with diethyl ether, dichloromethane, or other organic solvents, but also in the pharmaceutical and cosmetics in the determination of the optimal addition of preservatives that accumulate in emulsions particularly in the lipophilic phase, but As the hydrophilic phase will be effective.