When the reduction of aluminic oxide by carbon is conducted without the addition of copper, a brittle product is obtained that behaves in many respects like pig iron as it comes from the blast furnace. The same product is formed in considerable quantities, even when copper is present, and frequently the copper alloy is found embedded in it. Graphite is always found associated with it, even when charcoal is the reducing material, and analysis invariably shows a very high percentage of metallic aluminum. This extremely interesting substance is at present under examination.
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The use of electricity in the reduction of metals from their ores is extending so rapidly, and the methods of its generation and application have been so greatly improved within a few years, that the possibility of its becoming the chief agent in the metallurgy of the future may now be admitted, even in cases where the present cost of treatment is too high to be commercially advantageous.
The refining of copper and the separation of copper, gold, and silver by electrolysis have thus far attracted the greatest amount of attention, but a commercial success has also been achieved in the dry reduction by electricity of some of the more valuable metals by the Cowles Electric Smelting and Aluminum Company, of Cleveland, Ohio. Both this method of manufacture and the qualities of the products are so interesting and important that it is with pleasure we call attention to them as steps toward that large and cheap production of aluminum that the abundance of its ores and the importance of its physical properties have for several years made the unattained goal of many skillful metallurgists.
The Messrs. Cowles have succeeded in greatly reducing the market value of aluminum and its alloys, and thereby vastly extending its uses, and they are now by far the largest producers in the world of these important products. As described in their patents, the Cowles process consists essentially in the use for metallurgical purposes of a body of granular material of high resistance or low conductivity interposed within the circuit in such a manner as to form a continuous and unbroken part of the same, which granular body, by reason of its resistance, is made incandescent, and generates all the heat required. The ore or light material to be reduced—as, for example, the hydrated oxide of aluminum, alum, chloride of sodium, oxide of calcium, or sulphate of strontium—is usually mixed with the body of granular resistance material, and is thus brought directly in contact with the heat at the points of generation, at the same time the heat is distributed through the mass of granular material, being generated by the resistance of all the granules, and is not localized at one point or along a single line. The material best adapted