GB761280A - Improvements in and relating to methods of extracting sodium from amalgams - Google Patents

Abstract

761,280. Extracting sodium from amalgams. SOLVAY & CIE. May 25, 1954 [June 22, 1953], No. 15448/54. Class 82(1) Sodium is recovered from a dilute sodium-mercury amalgam by first raising the sodium concentration of the dilute amalgam to at least 0.39 gram. atom Na/ gram. atom (Na + Hg), and then supplying the concentrated amalgam so obtained to the top of a fractionating column operating at an absolute pressure between 0.36 and 26 m.m. mercury and at a base temperature which is equal to or greater than a minimum value which is a linear function of the sodium concentration of the amalgam supplied, the minimum value being 600‹C. at a sodium concentration of 0.39 gram. atom Na/gram. atom (Na + Hg), and 400‹C. at a sodium concentration of 0.48 gram. atom Na/gram. atom (Na + Hg). The operating pressure of the fractionating column corresponds to an operating temperature range of 400-600‹C. so that the column may be operated under conditions corresponding to any point within the shaded area of Fig. 1. The dilute amalgam is preferably obtained by electrolysis of an aqueous solution of a sodium salt, e.g. sodium chloride, in a mercury cathode cell. In one arrangement of apparatus described for carrying out the process, the sodium concentration of the dilute amalgam is raised to the desired value in a pair of stills in series and this concentrated amalgam is passed to the fractionating column the distillate from the first still being returned to the electrolytic cell and the distillates from the second still and the fractionating column being recycled to the foot of the first still. In another arrangement of apparatus, the sodium concentration of the dilute amalgam is raised by a single film evaporator and the distillates from the film evaporator and the fractionating column are recycled to the electrolytic cell.