Page:The New International Encyclopædia 1st ed. v. 01.djvu/488

ALUMINA. in dyeing. Its silicate forming a plastic mate- rial with water, it is extensively used in the manufacture of pottery. Corundum, sapphire, and ruby have been artificially made in Paris from alumina.

AL'UMIN'IUM or ALU'MINUM (From Lat. ahiiitcii, alum I. A metallic element, next to oxy- gen and silicon the most widely distributed. It is not found native, but in combination, chiefly as an oxide in the mineral corundum; as a hydrated oxide in diaspora; and in combination with oxy- gen and metals as aluminates, as in spinel, chrysobeiyl, and gahnite. 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 lluoride). The elementary nature of aluminium was recognized by Davy and others, but the metal was not iso- lated until 1S28, when Wohler succeeded in de- composing aluminium chloride by the action of potassium. Deville, in 1854, obtained the metal bj' electrolysis. A year later he simplified the process of manufacture by using sodium instead of potassium as a reducing agent. Devillc's ex- periments attracted the attention of Napoleon III., under whose patronage a metallurgical plant was established at .Tavelle. France. Ingots of the metal were exhibited at the World's Fair held in Paris, 1855. In 188G Hamilton Y. Cast- ner, of New York City, invented an important process for the reduction of aluminiiun. His patent, which was the first to be taken out since 1808, was for an improved method of obtaining sodium. He 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 aluminium. Jlc.nwhilp, Charles il. Hall, of Pittsburg, Pa., perfected an electrolytic method for tiic reduction of aluminium. In his process the alumina is held in solution by a molten fluoride hath, which is itself not decom- posed by the electric current. The latter is con- veyed to the melted solution by means of carbon cj'linders placed in the bath for positive elec- trodes, a carbon lined pot forming the negative electrode. The oxygen of the aluminium goes ofT at the positive electrode as carbon dioxide, wear- ing away the carbon at the rate ot 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 aluminiimi by the Hal! process were estalilished 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 from the Falls, a large electrolytic plant was erected at Niagara. The total production of aluminium in 1899 was 5,570.:)8 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 ahnninium in 1900 in the United States was 7.150,000 pounds, valued at $2,288,000, as against 1)1.281 pounds valued at $01,281, in 1890. In 1855, the first year of its commercial existence, aliuniniinn sold at $90 per pound; in 1870 it was $12 jicr pound: in 1SS9 the Pittsburg Reduction 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 (sjtu. A1., at. wgt. 27.11) is a white metal with a bhiish 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 cast iron, breaking at 15.000 pounds to 20.000 pounds per square inch, but 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 2ti,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 38, with copper at 73. G, and silver at 100. It is also sonorous. Aluminium is a little softer than silver, but its ductility allows it to be drawn, punched, or spun into almost any form. It is practically non-tarnishable, but strictly speak- ing, after long exiiosure to the atmosphere, its polish becomes dulled by a very thin film of white oxide. Aluminium is not acted upon by hydro- gen disulphide, carbon monoxide, carbon dioxide, or sulphurotis acid. It is practically unaffected b)' common salt, either wet or dry, and hence by sea water. On the other hand, solutions of the caustic alkalies readily attack it, and liydro- chloric 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 which they are worked. (See Alloys.) Those with copper arc called alumin- ium bronzes, and those with silver are known as ticiK (irrfi'iit. The lightness of metallic alumin- ium, subsequent to the improved processes for its manufacture, suggested its application as a sub- stitute for iron, tin. 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 eqtial conduc- tivity with copper cm be secured without undue weight, and the question seems to be largely one of expense, with the advantage at present in favor of aluminium.

BiBLlOGRAriiT. C. and A. Tissier. L' Alumin- ium Pt Jcs mctaux alcnlius (Paris. 1858); .1. W. Richards, Aiuminiiini. Itx Properties. Metalhirqii. and Alloys (Philadelphia, 1890); A, E. Hunt, J. W. Langlcy, and C. JI. Hall. "The Properties of Aliiiiiinum, with some Information Relating to the Jletal," Tratis<ictioi)S of the American Insti- tute of Mininij Enfiineers (New York, 1890). See ;.

AL'UM ROOT. A name given in the United States to two ]ilants, very different from one another, but agreeing in the remarkable astringency of their roots. One of these. Geranium maculatum (see Oeranh'M), very much resembles some of the species of Geranium which are common weeds in Great Britain, The root contains 12.27 per cent, tannin, gallic acid, pectin, and red coloring matter. The tincture of the root is of use in sore throat and ulcerations of the mouth, and is also administered in vari-