A process used to separate isotopes using electrolysis. It was once used to separate deuterium and hydrogen from water since hydrogen is more readily formed at the cathode than deuterium causing an enrichment of the water with deuterium oxide or heavy water.
(p. 123) http://www.visitvemork.com/no/vemork Official website of the Norsk Industriarbeider Museum, Vemork (Norwegian Industrial Workers Museum).