Radioactive Tracer Studies of Industrial Processes for the Electrolytic Refining of Aluminium and the Silicothermic Production of Magnesium

The authors consider the possibility of producing 99.999% pure aluminium by double electrolytic refining and of increasing the purity of silico- thermic magnesium by modifying the conditions under which the calcined dolomite is reduced and the vapours liberated are condensed. Applying the method based on three melted layers, they made a study of the industrial-scale electrolytic refining of aluminium, using the radioisotopes 59Fe, 64Cu, 69Znm, 72Ga, 114In, 115Cd and 178Au from its impurities. By adding 24Na-labelled cryolite to the electrolyte, they determined the part played by that element in the mechanism by which current is transferred to the cathode and to the anode. The interpretation of the results is based on the theory of the formation of polyionic combinations and complexes and their effect on the mobility of ions of different impurities during the electrolysis of the melted salts. In the case of magnesium, they studied the mechanism of materials passage in rotating dolomite calcination furnaces and also the processes of thermal reduction of calcined dolomite and of the condensation of vapours from impurities in the vacuum furnace used for the production of silicothermic magnesium. In this work they used dolomite activated in a reactor (to obtain radioactive sodium by activation of its impurity, sodium carbonate); also, labelled oxides of zinc and copper and labelled sodium carbonate. (author)