Processes leading to the alteration of isotope composition in a substance, e.g.: H2S + HDO → HDS + H2O (H = "normal" hydrogen, D = deuterium, "heavy" hydrogen, S = sulphur). The equilibrium is influenced by the different relative atomic masses
Winfried Koelzer, Nuclear Terms, Karlsruher Institut for Technologie KIT (Ed.), ISBN German print version 2001: 3-923704-32-1, Translation by Informationskreis KernEnergie (Berlin), Karlsruhe, Germany 2013. https://www.euronuclear.org/info/encyclopedia/pdf/ Nuclear_Glossary-%202013-02-13.pdf, (Nucl Sfty - Amer) {1011}