Heterogeneous exchange of precipitates

Summary

The calculation of fraction exchange is given for the case when the composition of the system changes during the heterogeneous exchange experiment.

In order to avoid essentially wrong conclusions, the change of specific activity of the liquid phase originating from heterogeneous exchange ought to be distinguished from the change originating from any other simultaneous process.

Two cases were considered: I. an inactive solid phase dissolving during the experiment, the liquid phase being previously labelled, and II. the solid phase formed during the experiment from exchangeable substance previously labelled in the liquid phase.