ELECTROCHEMICAL SENSOR FOR MEASURING MAGNESIUM CONTENT IN MOLTEN ALUMINUM

Design, construction, and tests of magnesium electrochemical sensors u sing molten salt electrolytes and pure magnesium metal reference are d escribed. Alumina as well as magnesia membrane thimbles were synthesiz ed to use as the supporting matrixes for the liquid electrolytes. Bina ry as well as ternary salt mixtures containing MgCl2 were impregnated in thimbles of various pore sizes, The accuracy, response time, and se rvice life of the sensors were evaluated. The magnesium contents from the electromotive force (e.m.f.) measurements were comparable with tho se from the atomic absorption analysis. All sensors responded instantl y to the changes of magnesium concentration in aluminium melt. The ser vice life was between 2 to 6 h and the minimum initial equilibration t ime was 2 min, depending mainly on the pore size of the magnesia thimb le and the electrolyte salt mixture in use.