J. Chim. Phys.
Volume 60, 1963
|Page(s)||259 - 262|
|Published online||28 May 2017|
Isotope effects in solid Li2SO4 at 600-790 °C
Department of Physics, Chalmers Institute of Technology, Göteborg, Sweden., Sweden..
Three different isotope fractionation processes have been studied in the same experiment, when solid Li2SO4 was electrolysed in a Vycor cell using a liquid zinc cathode and a gold anode. The main object was to study the enrichment of 7Li at the anode due to the difference in ion mobility. For this electromigration process the mass effect (i. e. relative difference in ion mobility/relative difference in mass) was µ = - 0,14, independent of temperature. The mass effect is thus about the same as in molten lithium halides. The principal difference between electromigration experiments in solid and molten salts is that in the former the salt lattice forms the « separation column », which is gradually consumed during the run, while for a melt the hydrostatic forces produce a counterflow which keeps the separation column filled with salt.
The two other isotope effects were found for the competing cathode reactions. Thus a lithium-zinc alloy was formed due to a deposition reaction while, simultaneously, reduction reactions gave a mixture of lithium oxide, sulfide, and also some sulfite. As to the deposition reactions, 6Li was enriched in the alloy with a separation factor of 1,01. The detection of an isotope effect for the reduction reactions was complicated by the fact that the reaction products were thoroughly mixed with remaining sulfate. However, a fraction of the products was insoluble in water, and a significant difference in isotope abundance was established between the soluble and the insoluble material.
© Paris : Société de Chimie Physique, 1963