Saito [SI] has patented separation of lithium isotopes by countercurrent exchange between lithium amalgam and lithium chloride or bromide dissolved in dimethyl formamide or other organic solvent. Arkenbout [A2] has measured a separation factor of 1.05 for this process, with 6 Li concentrating in the amalgam phase. With countercurrent flow through a packed column, natural lithium (7.5 percent 6Li) was separated into 5.8 percent 6Li at the top of a 1-m column and 12 percent 6 Li at the bottom. Reflux at the bottom was obtained by making the amalgam the anode (positive electrode) of an electrolytic cell in contact with the organic solution of the lithium salt. Reflux at the top was obtained by crystallizing lithium salt from organic solvent, dissolving it in water, and electrolyzing the aqueous solution at a mercury cathode.

Saito and Dirian [S2] have patented separation of lithium isotopes by countercurrent exchange between lithium amalgam and an aqueous solution of lithium hydroxide, with 6 Li concentrating in the amalgam phase. Reflux at the bottom is obtained by making the amalgam the anode of an electrolytic cell against an aqueous solution of LiOH. Reflux at the top is obtained by the reverse reaction, which takes place spontaneously between lithium amalgam and water. The simpler cathodic process is an advantage of this system compared with the previous one using an organic solvent. A disadvantage is the spontaneous transfer of lithium from amalgam to aqueous phase by chemical reaction that takes place as amalgam flows through the column. This has to be reversed by applying a negative potential to the amalgam either continuously or at intervals. Saito and Dirian report a separation factor of 1.06 to 1.07. Collin [CIO] reports 1.069 ± 0.004. A process like this was used in the Y-12 plant of the U. S. AEC.