AL'UMIN'IUM or ALU'IVIINUNI (From Lat.. (annum, alum A metallic element, next to oxy gen and silicon the most widely distributed. It is not found native, hut in combination, chiefly as an oxide in the mineral eorundum ; as a hydrated oxide in diaspore; and in combination with oxy gen and metals as aluminates, as in spine], ehrysoberyl. and galenite. It also occurs as a silicate in various clays. Its chief ores are bauxite (a hydrated aluminium oxide). and cryo lite an aluminium and sodium fluoride). The elementary nature of aluminium was recognized by Davy and others, but the metal was not iso lated until 1328, when \Voider succeeded in de composing almninium chloride by the action of potassium. Deville, in ]S54, obtained the metal by electrolysis. A year later he simplified the process of manufacture by using sodium instead of potassium as a reducing agent. Deville's ex periments attracted the attention of Napoleon III., under whose patronage a metallurgical plant was established at Javelle, France. Ingots of the metal were exhibited at the World's Fair held in Paris, 1855. In 1886 Hamilton Y. Cost ner, of New York City. invented an important process for the reduction of aluminium. His patent, which was the first to be taken out. since 1808, was for an improved method of obtaining sodium. Ide succeeded in lowering the price of that reducing agent from one dollar a pound to one-fourth that amount. He established a plant in Oldbury, England, and began the commercial production of almninium. Me“nwhile, Charles M. Hall, of Pittsburg, Pa., perfected an electrolytic method for the reduction of aluminimn. In his process the alumina is held in solution by a molten fluoride bath, which is itself not decom posed by the electric current. The latter is con veyed to the melted solution by means of carbon cylinders placed in the bath for positive elec trodes, a carbon lined pot forming the negative electrode. The oxygen of the aluminium goes off at the positive electrode as carbon dioxide, wear ing away the carbon at the rate of nearly a pound of carbon to the'pound of aluminium produced. The reduced metal settles at the bottom of the pot, which is easily tapped, yielding a metal of 99 per cent. purity. Works for the reduction of aluminium by the Hall process were established in 1889 near Pittsburg. Since then Pittsburg has been the centre of the aluminium industry in the United States; although in 1895, taking ad vantage of the power obtained front the Falls, a large electrolytic plant was erected at Niagara. The total production of aluminium in 1899 was 5,570.38 metric tons, about 12,254,838 pounds, of which the Pittsburg Reduction Company of Niagara Falls, N. Y., produced about 2948 metric tons, about 6,500.000 pounds. The production of aluminiinn in 1900 in the United States was 7.150,000 pounds, valued at $2,288,000, as against 61,281 pounds valued at $61,2.81, in 1890. In 1855, the first year of its commercial existence. aluminium sold at $90 per pound: in 1870 it was $12 per pound; in 1889 the Pittsburg Reduetion Company sold it at $2 per pound, and in 1899 aluminium in rods and bars for electrical conduction was sold at 29 cents per pound.
Aluminium (sym. Al., at. wgt. 27.11) is a white metal with a bluish tinge, is extremely malleable, and has a specific gravity of 2.56, which may be increased to 2.68 by rolling. In its tensile strength it ranks with east iron, breaking at 15,000 pounds to 20,000 pounds per square inch, hut in malleability and ductility it ranks with gold. Like gold and silver, it hard ens in working, and rods and wire vary in strength from 26,000 pounds to 62,000 pounds'per square inch. The electrical conductivity of alu minium is about 50, with copper at 90, and silver at 100; and its thermal conductivity is 3S, with copper at 73.6, and silver at 100. It is also sonorous. Aluminium is a little softer than silver. hut its ductility allows it to be drawn, punched, or spun into almost any form. It is practically non-tarnishable, hut strictly speak ing, after long exposure to the atmosphere, its polish becomes dulled by a very thin film of white oxide. Aluminium is not acted upon by hyd•o gen disulphide, carbon monoxide, carbon dioxide, or sulphurous acid. It is practically unaffected by common salt, either wet or dry, and hence by sea water. On the other hand, solutions of the caustic alkalies readily attack it, and hydro chlo•ic acid is its natural solvent. Aluminium forms alloys with most of the metals. Those with copper, silver, and tin are much used on account of their color. hardness, and stability, and the ease with while!' they are worked. (See Au.ovs.) Those with copper are called alumin ium bronzes. and those with silver are known as tiers ardent. The lightness of metallic alumin salisequent to the improved processes for its manufacture, suggested its application as a sub stitute for iron, till, or copper; but as yet it has failed to supersede any of these metals, on ac count of its high price. Its most important use is still in the form of alloy, especially with cop per; but it has received growing favor in the manufacture of cooking and table utensils, and as a substitute for heavier metals in opera glass mountings and other optical instruments. An application of aluminium that promises favor ably is in the manufacture of accoutrements for military purposes. Aluminium is enjoying an increased use for electrical conductors as a sub stitute for copper. Owing to its lightness, the necessary cross section to insure equal conduc tivity with copper can lie secured without undue weight, and the question seems to be largely one of expense, with the advantage at present in favor of aluminium.
BinuounAeuv. C. and A. Tissier, L'A/nmin him ct lcs nOgux alcolins (Paris, 185S) ; Richards, Aluminium, Its Properties, Metallurgy, and Alloys (Philadelphia, 1S90) : A. E. Hunt, J. \V. Langley, and C. M. Hall, "The Properties of Aluminum, with some Information Relating to the Metal," Transuelio»s of the American Insti tute of Mining Engineers (New York, 1890), Sec BAUXITE CRYOLITE.