Abstract: A method of disposing of silica dust recovered from the smoke of metallurgical furnaces by producing aluminum fluoride therefrom for use in electrolytic melting furnaces is disclosed. Fluorspar and the precipitated amorphous silicon dioxide are treated with steam at elevated temperatures whereby hydrogen fluoride-containing gases are produced and then these gases are passed through a layer of aluminum oxide. Part of the gaseous hydrogen fluoride will then react with the alumina to form aluminum fluoride and part of it will be adsorbed in the alumina whereby an intimate mixture of alumina and fluorine is obtained which is useful in electrolytic furnaces.