ENRICHMENT OF NA AND K OR LI-6 AND LI-7 BY COUNTER CURRENT FLOW OF THE COEXISTING PHASES OF NA K-AMMONIA OR LI-6/LI-7-AMMONIA SOLUTIONS/

Metal-ammonia solutions (M-AS) have a miscibility gap, they separate a t low temperatures into a diluted, electrolytic phase of high density and a concentrated, metallic phase of low density. In mixed sodium-pot assium solutions (Na/K-AS) after phase separation sodium is enriched i n the metallic phase, the separation factor alpha(Na/K) (Eq. (2)) is t he larger, the lower the temperature relative to the critical temperat ure of the miscibility gap or the wider the miscibility gap. Therefore in deuteroammonia solutions (DAS) with higher critical temperatures t he enrichment is more effective than in normal ammonia solutions. In L i-DAS with the two stable isotopes Li-6 and Li-7 the lighter one is en riched in the metallic phase. The separation factor (Eq. (4)) is alpha (Li) approximate to 1.010 at -73 degrees C. By multiplication of the s ingle equilibrium effect in a counter current column, which acts like a solvent-solvent extraction column, the species can be enriched. The counter current operation of the column was enforced by electrochemica l means (application of a dc-current through the column), and the enri chment was tested around -74 degrees C with equimolar Na/K-AS and Na/K -DAS for which alpha(Na/K) = 1.61 and 1.70 resp, and with Li-DAS of na tural Li-isotope abundance. The height of the theoretical plate of the column for all three systems was HTP = 12.9 +/- 0.3 cm.