CHANGES IN PRACTICE OF ALUMINUM MANUFACTURE
Heretofore bauxites low in silica (2 to 5 per cent. SiO2) have been used for the preparation of alumina for the manufacture of aluminum. Many experimenters have endeavored to utilize low-grade (high-silica) bauxites, or aluminum silicates for the recovery of alumina. These experiments show that it is chemically possible to produce low-silica alumina from many aluminous materials, but not on a commercially profitable basis. It seems reasonably certain that one or more of the methods of handling low-grade bauxite or even aluminous silicates will be developed to the commercial stage, even under ordinary conditions, in the near future. That event should tend to revolutionize the aluminum industry, as clays and shales carrying from 25 to 35 per cent. Al2O3 are of widespread occurrence. Whether it would materially lower the price of aluminum is more doubtful, for the costs of manufacture would be raised by the increased cost of treating the low-grade crude material.