Isotope effects of barium in amalgam aqueous hydroxide solution systems

Isotope effects of barium in amalgam/aqueous hydroxide solution systems have been studied. Two types of isotope effects with opposite isotope enrichment directions have been observed in the electrolytic process, where barium is transferred from the aqueous phase into the amalgam phase under a constant electrolytic voltage. The isotope effect leading to the enrichment of the heavy isotope in the amalgam phase is caused by the equilibrium mechanism, while the isotope effect leading to the enrichment of the light isotope in the amalgam phase has been suggested to be caused by a kinetic mechanism. The equilibrium isotope effect has been investigated by single- and multi-stage techniques in the range 294-349 K and has been found to increase with increasing temperature. In the equilibrium state at 308 K, the separation coefficient for isotopes differing by one unit of mass has been determined as (-4.2 +/- 1.4) x 10(-4).