GB517455A - Improvements in or relating to the conversion of alkaline earth metal oxalates and the manufacture of alkali metal hydroxides - Google Patents

Abstract

517,455. Metal oxalates; ammonium compounds containing metals; alkali manufacture. CLIFFORD, I. L., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. July 28, 1938, No. 22531. [Classes 1 (ii) and 1 (iii)] [Also in Group IV] Solutions of the oxalates or oxalate ammines of metals such as copper, zinc, nickel, silver, cobalt and cadmium are obtained by treating an alkaline earth metal oxalate with an oxide or hydroxide of the metal of which the oxalate is required and with sufficient carbon dioxide to convert the alkaline earth metal into carbonate, in the presence of an aqueous medium containing sufficient ammonia or other volatile alkali to render the desired metal oxalate or oxalate ammine soluble. The precipitated alkaline earth carbonate may be separated, and the' solution partly distilled to precipitate the oxalate or oxalate ammine, the solution remaining being re-used in the process. The metal oxide or hydroxide may be treated with carbon dioxide and volatile alkali before addition of the alkaline earth metal oxalate. The above process may be incorporated in a modification of the process of Specification 477,230 for the production of alkali metal hydroxides from alkali metal salts, e.g., chlorides, nitrates and sulphates. The alkali metal salt is reacted with copper or like oxalate in the presence of water and volatile alkali, the precipitated alkali metal oxalate is removed and causticised with alkaline earth metal oxide or hydroxide, and the precipitate of alkaline earth metal oxalate is removed and reacted according to the above process with copper or like oxide or hydroxide in the presence of carbon dioxide and volatile alkali; the metal oxide or hydroxide for this last step is obtained by distillation in the presence of alkaline earth, of the mother liquor separated from the alkali metal oxalate, any insoluble alkaline earth salt, e.g., sulphate, admixed with the precipitated oxide or hydroxide being removed before addition of the calcium oxalate.