ALUMINUM or ALUMINIUM. Webster and Worcester sanction either way of spell ing—Webster giving aluminum " us preferable, Worcester v aluminium." German, alionitun ; I" Tench, alnmiaiinm. In England, aluminium has the preference. In America, aluminum is most used, and the shorter !Mine aliNto is being strongly urged in preference to either. Chemi cal symbol, Al. Atomic weight, 27.02. Aluminum group, aluminum, indium, gallium. These metals form feebly basic sesquioxides, which act toward stronger bases as acid-forming oxides.
Orruircnre of Aftimininn in Nallire.—Of all the elements :aluminum is the most widely distributed and contained in t he largest quantity in the solid crust of the earth, except oxygen and silicon. Its ores from which pure alumina is obtained, from which the pure metal is extracted, are: Bauxite soft and granular, with 5n to 70 per cent of oxide of alu minum, and with only a few per c•eut of accidental impurities besides the Water of hydra tion. Corundum (.11,(1,), very hard and crystalline, specific gravity 3.900, with 03 pet• cent alumina-, and ordinarily very I'rac from impurities, so luml and crystalline, and withal so valuable for other pnrposys, ns not to be at present used is an aluminum ore. Diaspore (.112(1811,0), hard and arystalline; spvt.ifiv gravity with 65 to 55 per cent alumina, and ordinarily very pure. eryolite specific gran•ity with 10 per cent tilmeinum fluoride and 611 per Cent sodium fluoride, Alnininite (AI,S0,0I1,0), specific gravity 1.66, ronito ming some :Hi tier remit of idumina in a condition, by roasting. solution, and filtration, to be cheaply purified. ttitrbsite (A1,0311,0), stalactitie; specific• gravity 2.4. con taining 6.1 per cent alumina. The oxide of aluminum occurs largely in combination with silica, chiefly as double silicates, of which orthoclase or potash feldspar is most important, forming the chief constituents of granite. gneiss, syenite, porphyry, trachyte, etc. Soda feldspars and lime feldspars also occur in the large garnet and mica groups of minerals, both double silicates of aluminum. Weathering, of feldspars has formed the clays which are silicates 'of aluminum. Neither feldspars or clays, however, are economical ores, in com parison with those given above, for the production of aluminum, on account of the difficulty of separation from the silica. Aluminum is shown by the spectroscope as being present in the solar atmosphere.
Chemical Properties.—Aluminum-leaf decomposes water at 100°, and, heated in oxygen gas. burns with an intense white flame. The resulting compound, however, shows the metal not to have been completely burned to an oxide, but to have been protected by a surface coat ing. The metal dissolves in aqueous solutions of alkalies ; with the evolution of hydrogen, deposits lead, silver, and zinc from alkaline solutions, while neutral or acid solutions are not altered by it. It precipitates copper from a solution of sulphate of copper. Hydrochloric acid is its best solvent. Concentrated sulphuric acid dissolves aluminum on heating, with evolu tion of sulphurous acid, dilute sulphuric acid acting only very slowly on the metal. The pres ence of any chlorides in the solution, however, allows it to be rapidly decomposed. Nitric acid, either concentrated or dilute. has very little action on aluminum. Organic acids attack the metal only slightly. Sulphur has no action on it at a temperature less than a red-heat. Aluminum is not acted upon by carbonic acid or carbonic oxide gases, nor sulphureted hydrogen, but it is a peculiarity of the metal in a melted condition to absorb large quanti ties of these gases, a portion of which is again excluded on the metal cooling, but enough being left., in the case of sulphureted hydrogen, to continue to emit a strong odor for a long time after solidifying. Aluminum is little acted upon by salt water; and even solutions of salt and vinegar, such as the metal is likely to be subjected to in certain culinary operations, do not seem to practically injure the metal. It is less acted upon than tin, copper, or silver under similar conditions. Aluminum is found to withstand the actions of organic secre tions better than even silver. and it is largely used for surgical and dental instruments. So lutions of caustic alkalies, chlorine, bromine, iodine, and fluorine, rapidly corrode aluminum.
Ammonia gas has very little action upon the metal except to turn it to a gray color. Strong aqua-ammonia, has a slight solvent action upon it. Pure aluminum does not tarnish from the influence of the weather, except very slowly, even though the atmosphere be moist, or even salt. Instead of retaking oxygen, like the metals of the alkalies and alkaline earths, with an en ergy proportioned to the extreme difficulty with which it departs from its oxygen in the state of oxide. aluminum is almost as indifferent to oxygen as are gold and platinum. The strong affinity of aluminum and oxygen before separation, contrasted with their apparent total indif ference afterward, may be explained by the existence of a thin film of oxide, which almost immediately forms upon the exposure of the metal to the atmosphere, and protects it from further oxidation. The resistance of aluminum to atmospheric influences, and its anti-eorrodi bility, are among its most noted qualities. The presence of silicon in alninintnn materially detracts from its power to withstand corrosion. Aluminum containing sodium is rapidly acted upon by hot water, the sodium being eaten out, leaving the aluminum spongy and porous. Aluminum or aluminum compounds do not impart any color to the non-luminous gas-flame. The sitark-spectrum of aluminum has been mapped, and contains a large number of bright lines lying close together, of which the most important in the red are 6.4;23 and 6,425, and in the blue 4,061 and 4,602 and the alunffninn hands seen in the ultra-violet are extremely characteristic. heated in an atmosphere of chlorine gas. aluminum burns violently to a chloride. Aluminum melts at a temperature between silver and zinc—a temperature of Q00° C. (authority, Roscoe); 1,300' F. (authority. Richards). The metal becomes pasty at about 1.000° F.. and loses its tensile strength and very much of its rigidity at a temperature between 400° and 500' F., although this rigidity and strength are almost entirely regained as the metal cools. Aluminum does not volatilize at any temperature ordinarily to be pro duced by the combustion of carbon, even though the high temperature be kept up for a con siderable number of hours' time. It, however, absorbs a very large amount of occluded gases by such treatment. '1'lle impurities most commonly found in aluminum are silicon and iron; and it may be said of the electrolytically made metal that these two impurities are almost the only ones found, considerable amounts of any others being accidental. A large proportion of the aluminum being made by the newer electrolytic processes. runs over 99 per cent pure aluminum, the impurities coming simply front the alumina ore and the ash of the carbon elec trodes. the impurities in the reagent solvents for the alumina being reduced and alloyed with the first metal made. Silicon in aluminum exists in two forms, one seemingly combined with the aluminum as combined carbon exists in pig-iron, and the other in an allotropic graphitoi dal modification. These two forms of the silicon seem to exert considerably different effects by their presence in the aluminum, the combined form of the element rendering the metal much harder than the graphitoidal variety. The combined modification ordinarily prepon derates. and is usually from 55 to SO per cent of the total silicon. The presence of iron as an impurity in aluminum is more easily avoided, and, by taking care in the use of tools and that the grinding of the carbon is done with good stone wheels, its presence is very often a mere trace. For many purposes the purest aluminum can not be so advantageously used as that containing from 3 to 6 per cent impurities, as the pure metal is very soft, and not so strong as the less pure. It is only where extreme malleability, ductility, or non-corrodi bility is required that the purest metal should be used. For most purposes small amounts of some of the other metals than silicon and iron are advantageously added, to produce hardness. rigidity. and strength—constituents that will not detract from the non-eorrodi bility of the metal as much as do these natural impnrities that come from the ore and appa ratus.