this, Messrs. Cowles place what may be called a stuffing box around them, consisting of a copper box filled with copper shot. The wires are attached to the boxes instead of the electrodes. The hot electrodes as they emerge from the furnace first encounter the shot, which rapidly carry off the heat, and by the time they emerge from the box they are too cool to be oxidized by contact with the air. 66 Ninety horse-power have been pumped into the furnace for five hours. At the beginning of the operation the copper first melted in the centre of the furnace. There was no escape for the heat continually generated, and the temperature increased until the refractory corundum melted, and being surrounded on all sides by carbon gave up its oxygen. This oxygen, uniting with the carbon to form carbonic oxide, has generated heat which certainly aids in the process. The copper has had nothing to do with the reaction, as it will take place in its absence. Whether the reaction is due to the intense heat or to electric action it is difficult to say. If it be electric, it is Messrs. Cowles's impression that we have here a case where electrolysis can be accomplished by an alternating current, although it has not been tried as yet. Were the copper absent, the aluminium set free would now absorb carbon and become a yellow, crystalline carbide of aluminium; but, instead of that, the copper has become a boiling, seething mass, and the bubblings of its vapors may distinctly be heard. The vapors probably rise an inch or two, condense and fall back, carrying with them the freed aluminium. This continues till the current is taken off the furnace, when we have the copper charged with 15 to 30 per cent., and in some cases as high as 40 per cent. of its weight of aluminium, and a little silicon. After cooling the furnace this rich alloy is removed. A valuable property of the fine charcoal is that the metal does not spread and run through its interstices, but remains as a liquid mass surrounded below and on the sides by fine charcoal which sustains it just as flour or other fine dust will sustain drops of water for considerable periods, without allowing them to sink in. The alloy is white and brittle. This metal is then melted in an ordinary crucible furnace, poured into large ingots, the amount of aluminium in it determined by analysis, again melted, and the requisite amount of copper added to make the bronze desired. "Two runs produce in ten hours' average work 100 pounds of white metal, from which it is estimated that Cowles Bros., at Lockport, are producing aluminium in its alloys at a cost of about forty cents per pound. The Cowles Co. will shortly have 1200 horse-power furnaces. With a larger furnace there is no reason why it should not be made to run continuously like the ordinary blast furnace. "In place of the copper any non-volatile metal may be used as a condenser to unite with any metal it may be desired to reduce, provided, of course, that the two metals are of such a nature that they will unite at this high temperature. In this way aluminium may be alloyed with iron, nickel-silver, tin, or cobalt. Messrs. Cowles have made alloys containing 50 Al and 50 Fe, 30 Al, and 70 Cu, 25 Al and 75 Ni. Silicon or boron or other rare metals may be combined in the same way, or tertiary alloys may be produced; as, for instance, where fire clay is reduced in presence of copper we obtain an alloy of aluminium, silicon, and copper. This alloy is white and brittle if it contains over ten per cent. of aluminium and silicon together. With from two to six per cent. of these two, in equal proportions, the alloy is stronger than gun-metal, has great toughness, does not oxidize when heated in the air, and has a fine gold color. I hear to-day that an aluminium-silicon bronze wire made by Cowles has shown a tensile strength of 200,000 pounds, hitherto unprecedented in any metal. "As to the ores of aluminium. For Mitis catsings, where iron and silicon are not prejudicial, beauxite or various clays may be used to advantage. For bronze making, alumina containing silica in considerable quantities is as available as the pure earth and is indeed superior to it." To manufacture pure aluminium, pure alumina is necessary. Cowles Bros. use corundum obtained from Northern Georgia. (See p. 49.) REDUCTION BY IRON. The statement has been made* that aluminium sulphide, Al'S3, is to be obtained from powdered cryolite by treating it with water, which dissolves out sodium fluoride, NaF, and the residual A12F being calcined with sulphide of lime, CaS, there results A12S3 and CaF2. The A12S3 is then decomposed by heating to redness with iron turnings. According to a patent given to F. Lauterborn,† Germany, Aug. 14, 1880, if pulverized cryolite is boiled with water, NaF is set free and A12F6 remains. Likewise, calcium fluoride, CaF2, boiled with A12C16 gives CaCl2 and A12F6. The aluminium fluoride by heating with sulphide of lime will be converted into A12S3. Finally, the A12S3, by heating red hot with iron gives, it is claimed, metallic aluminium. The above are all the details of this process to be found. See in the Appendix an experiment on thus decomposing cryolite. H. Niewerth has patented the following process: "Ferro-silicum is mixed with A12F6 in proper proportions and the mixture submitted to a suitable red or melting heat by which the charge is decomposed into volatile silicon fluoride, SiF4, iron, and aluminium, the two latter forming an alloy. *Chemical News, 1860. + Dingler, 242, p. 70. Sci. Am. Suppl. Nov. 17, 1883. In order to obtain the valuable alloy of aluminium and copper from this iron-aluminium alloy, the latter is melted with metallic copper, which will then by reason of greater affinity unite with the aluminium, while the iron will retain but an insignificant amount of it. On cooling the bath, the bronze and iron separate in such a manner that they can readily be kept apart. In place of pure Al2F, cryolite may advantageously be employed, or Al2C16 may also be used, in which case silicon chloride volatilizes instead of the fluoride. Or, again, pure silicon may be used with A12F6, cryolite, or Al2Cl, in which case pure aluminium is obtained." Preparation of Aluminium and Sodium im the According to the experiments of Mr. W. P. Thompson,* sodium and aluminium may be advantageously prepared by means of a Bessemer converter. The same process it seems should serve equally well for the preparation of the other difficultly reducible metals, such as calcium, strontium, barium, magnesium, etc. Mr. W. P. Thompsont has taken out a patent in England for the manufacture of aluminium and similar metals, which is carried out as follows: The inventor employs as a reducing agent iron, * Bull. de la Soc. Chem. de Paris, 1880, xxiv. 128. |