For the interpretation of connections between the amount of nitrogen and its isotopic composition in metamorphites and igneous rocks the knowledge of the separation factors of some interesting isolopic exchange processes is essential. On the basis of quantum mechanics several authors calculated interesting isotope effects. The aim of our investigation was to determine experimentally some of these calculated equilibrium constants. In the systemthe nuclide14N is enriched in the gaseous phase. In the systems CrN/N2and Ca3N2/N2the nuclide15N is enriched in the gaseous phase.