GB732906A - Improvements in and relating to the production of alkali metals and their hydroxides - Google Patents

Abstract

732,906. Electrolytic production of alkali metals and their hydroxides. EDIGER, W. VON. Nov. 4, 1952 [Nov. 5, 1951], No. 25812/51. Class 41. Apparatus for electrolytic production of alkali metals or their hydroxides from an aqueous solution of an alkali metal salt includes a partition, screen or barrier comprising a salt of the alkali metal being deposited, adapted to allow passage of metallic ions to the cathode assembly of the electrolysing plant while preventing the passage of water thereto. The production of sodium, potassium and lithium are referred to. The partition may be a thin sheet of a salt, e.g. NaCl or KCl or alternatively, a porous pot or the like in the pores of which, either before the electrolysis or during the early stages of which, a filling of the sodium or potassium salt is provided. The cathode may consist of the metal being produced, preferably molten. Means may be provided for the continuous removal of the metal as it is produced at the cathode; or if the hydroxide is being formed, means to set up a reaction between the metal and water. In this latter case the cathode assembly may include mercury. As shown in Fig. 1, a partition 2 of unglazed ceramic material separates a chamber packed with alkali metal 4 from another chamber containing a saturated salt solution and a carbon block anode 6. The anode chamber has a feed pipe 8 for replenishing the solution and an overflow pipe 9 to maintain the solution at a prearranged level. The cathode chamber is provided with a feed pipe 10 through which kerosene may be added to cover the alkali metal and an outlet 11 for leading off alkali metal to a receptacle 12 where it is also preferably covered by a layer of kerosene. On electrolysis, the pores of the ceramic barrier 2 become clogged with salt from the saturated solution which allows the passage of metallic ions from the solution to the cathode. If desired, the barrier may be pretreated to fill its pores with salt. If sodium or potassium hydroxide is to be produced, the metal initially present is replaced by mercury and the cathode compartment is almost completely occupied by a block of wood which confines the mercury to a thin layer adjacent the ion-pervious partition and a thin layer at the top of the compartment over the block, water covering the block in place of the kerosene. According to another modification a cylindrical vessel closed at one end and formed of unglazed ceramic material is packed with sodium or the like and immersed in a saturated aqueous solution of the salt being electrolysed. An iron rod or like conductive element forms contact with the sodium and it is covered with kerosene. A carbon rod dipping in the electrolyte forms the anode.