Current Efficiency Measurements in Laboratory Aluminium Cells—IV. Depletion of Alumina and Cell Voltage

AbstractThe performance of a 5 A laboratory aluminium cell was studied. The use of boron nitride parts in the cell tended to give erroneous results with respect to current efficiency (CE), probably due to reactions between the boric oxide binder and dissolved aluminium in the electrolyte. Electrode potentials were measured by means of an aluminium reference electrode. The observed rise in cell voltage as the electrolysis progressed was mainly due to increasing anode potential, caused by a local depletion of alumina in the melt adjacent to the anode, which provoked the anode effect after 2–3 h of electrolysis. The temperature dependence of the CE was measured between 935 and 1063°C. Resume Le rendement d'une pile experimentale en aluminium d'une capacite de 5 A a ete mesure. Certaines pieces de la pile etant assemblees avec du nitrure de bore, les mesures obtenues furent entachees d'erreur, ce qu'on peut problablement expliquer par une reaction du ciment a l'acide borique avec l'aluminium dissout dans l'el...