Relationship between distribution coefficients and equilibrium constants

RELATIONSHIP BETWEEN DISTRIBUTION COEFFICIENTS AND EQUILIBRIUM CONSTANTS 

Despite the apparently over-sin lified form of the Berthelot-Nernst distribution coefficient, it has been extensively employed in trace element geochemistry often with considerable success. In this respect it is instructive to compare D. with the true equilibrium constant for a given reaction. As an example the partition of Ni between olivine and clinopyroxene (Hakli and Wright, 1967 Broecker and Oversby, 1971 Banno and Matsui, 1973 Carmichael Consider the following exchange reaction  

If the Ni Concentrations are low the activities of the CaMgSi20g and Mg2Si0j components will be close to unity, and substituting from equation (l) for activities of the trace components. 

When one of the phases is a liquid phase, some insight into factors influencing can be gained by considering a reaction such as the following  

In this situation the left hand side which is related to depends not only on K and the Henry s Law constants k and k but also on a-  

---