ALUMINIUM
341
pecuniary assistance from the French Academy, and also from the an iron lid lined with firebrick was luted, in its place to exclude The charge was reduced by means of a 50-volt current from a hands of Napoleon III., who, impressed with an aluminium medal air. struck in his honour, and with a baby-rattle presented to the infant 300-kilowatt dynamo, which was passed through the furnace for Prince Imperial, conceived the idea of furnishing his Cuirassiers 14 hours till decomposition was complete. About 100 lb of with aluminium armour and helmets. For over a year the bronze, containing from 15 to 20 lb of aluminium, were obtained Emperor defrayed Deville’s expenses, and although the latter did from each run, the yield of the alloy being reported at about 1 lb not find it possible to gratify his patron’s military aspirations, yet per 18 e.h.p.-hours. The composition of the alloys thus produced, Napoleon III.’s generosity in assisting scientific research has borne could not be predetermined with exactitude , each batch was therefore analysed, a number of them were bulked together, or much fruit both in the western and eastern hemispheres. with copper in the necessary proportion, and melted in When Deville quitted the Javel works, two brothers named mixed Tissier, formerly his assistants, who had devised an improved crucibles to give merchantable bronzes containing between 1 j and sodium furnace and had acquired a thorough knowledge of their 10 per cent, of aluminium. Although the copper took no part in leader’s experiments, also left, and erected a factory at Amfreville, the reaction, its employment was found indispensable, as otherwise aluminium partly volatilized, and partly combined with the near Rouen, to work the cryolite process. This need not be the to form a carbide. It was also necessary to give the fine described at length. It consisted simply in reducing cryolite with carbon metallic sodium exactly as in Deville’s chloride method, and it was charcoal a thin coating of calcium oxide by soaking it in lime-water, claimed to possess various mythical advantages over its rival. Two for the temperature was so high that unless it was thus protected was gradually converted into graphite, losing its insulating grave disadvantages were soon obvious—the limited supply of ore, it and diffusing the current through the lining and walls of the and, what was even more serious, the large proportion of silicon in power furnace. this process did not depend upon electrolysis, but the reduced metal. The Amfreville works existed some eight or ten was simplyThat an instance of electrical smelting, or the decomposition years, but achieved no permanent prosperity. In 1858 or 1859 a an oxide by means of carbon at the temperature of the electricsmall factory, the first in England, was built by F. W. Gerhard of is shown by the fact that the Cowles furnace would work with at Battersea, who also employed cryolite, made his own sodium, arc, an alternating current. and was able to sell the product at 3s. 9d. per oz. This enterprise In 1883 Griitzel patented a useless electrolytic process with: only lasted about four years. Between 1860 and 1874 Messrs. fused or the double chloride as the raw material, and in Bell Brothers manufactured the metal at Washington, near New- 1886 cryolite Kleiner propounded a cryolite method which was worked, castle, under Deville’s supervision, producing nearly 2 cwt. per for a time the Aluminium Syndicate at Tyldesley near Manyear. They took part in the International Exhibition of 1862, chester, butbyw’as abandoned in 1890. In 1887 Minet took out quoting a price of 40s. per lb troy. for electrolysing a mixture of sodium chloride with In 1881 Webster patented an improved process for making patents fluoride, or with natural or artificial cryolite, a he alumina, and the following year he organized the Aluminium Crown aluminium was continuous, the metal being regularly run off from Metal Co. of Hollywood to exploit it in conjunction with Deville’s operation bottom of the bath, while fresh alumina and fluoride were method of reduction. Potash-alum and pitch were calcined the as required. The process exhibited several disadvantages together, and the mass was treated with hydrochloric acid ; char- added electrolyte had to be kept constant in composition lest eithei coal and water to form a paste were next added, and the whole was the vapours should be evolved or sodium thrown ilown, and dried and ignited in a current of air and steam. The residue, con- fluorine raw materials had accordingly to be prepared in a pure sisting of alumina and potassium sulphate, was leached with water the After prolonged experiments in a factory owned by Messrs to separate the insoluble matter which was dried as usual. Allron the state. Bernard Freres at St Michel in Savoy, Minet’s process was given by-products, potassium sulphate, sulphur, and aluminate of i > up, at the close of the 19th century the Heroult-Hall method were capable of recovery, and were claimed to reduce the cost of was and alone being employed in the manufacture of aluminium throughthe oxide materially. From this alumina the double chloride was out the world. prepared in essentially the same manner as practised at Salindres, The original Deville process for obtaining pure alumina from but sundry economies accrued in the process owing, to the larger bauxite wTas greatly simplified in 1889 by Bayer, whose most scale of working and to the adoption of Weldon’s method of recent patents are being exploited at Larne in Ireland. Crude regenerating the spent chlorine liquors. In 1886 Castner s sodium bauxite is ground, lightly calcined to destroy organic matter, and patents appeared, and The Aluminium Co. of Oldbury was pro- agitated under a pressure of 70 or 80 lb per square inch with a moted to combine the advantages of Webster’s alumina and solution of sodium hydroxide having the specific gravity 1 45. Castner’s sodium. Castner had long been interested in aluminium, After two or three hours the liquid r diluted till its density falls and v as desirous of lowering its price. Seeing that sodium was the to 1-23, when it is passed throughis filter-presses to remove the only possible reducing agent, he set himself to cheapen its cost, insoluble ferric oxide and silica. The solution of sodium and deliberately rejecting sodium carbonate for the more expensive containing aluminium oxide and sodium oxide in the aluminate, molecular sodium hydroxide (caustic soda), and replacing carbon by a mixture proportion of 6 to 1, is next agitated for thirty-six hours with small of iron and carbon—the so-called carbide of iron he invented the quantity of hydrated alumina previously obtained, which acauses highly scientific method of winning the alkali metal which has the liquor to decompose, and some / 0 per cent, of the aluminium remained in existence almost to the present day. In 18/2 sodium hydroxide to be thrown down. The filtrate, now containing lire pared by Deville’s process cost about 4s. per lb., the greater part roughly two molecules of alumina to one of soda, is concentrated of the expense being due to the constant failure of the retoits , m the original gravity of 1 ‘45, and employed instead of fresh 1887 Castner’s sodium cost less than Is. per lb, for his cast-iron to caustic for the attack of more bauxite ; the precipitate is then pots survived 125 distillations. ,, washed till free from soda, dried, and ignited at about In the same year Grabau patented a method of reducing the collected, 1000° C. to convert it into a crystalline oxide which is less hygrosimple fluoride of aluminium with sodium, and his process was scopic than the former amorphous variety. operated at Trotha in Germany. It was distinguished by the process of manufacture which now remains to be described unusual purity of the metal obtained, some of his samples contam- wasThepatented 1886 and 1887 in the name of C. M. Hall ing 99-5 to 99-8 per cent. In 1888 the Alliance Aluminium Co. in America, in during of P. Y. L. Heroult in England and France. was organized to work certain patents taken out during the previous It would be idlethat to discuss to whom the credit of first imagining year by Dr Netto, Capt. Cunningham, and Mr Forster for winning the method rightfully belongs, for probably this is only one of the metal from cryolite by means of sodium, but these were only the many occasions when new ideas have been born in several modifications in detail of the processes already described. This brains at the same time. Hall, however, at once realized^ that company erected plant in London, Hebburn, and Wallsend, and by his aim should be to win aluminium itself in an electrically 1889 were selling the metal at 11s. to 15s. per lb. The Alummiu warmed bath ; for a while Heroult seemed undecided between the Company’s price in 1888 was 20s. per lb and the pure metal and an alloy, between internal and external heating. 250 lb per day. In 1889 the price was 16s., but by 1891 the By 1888 Hall was at work on a commercial scale at Pittsburg, electricians commenced to offer metal at 4s. per lb and aluminium reducing German alumina; in 1891 the plant was removed to reduced with sodium became a thing of the past. _ Kensington for economy in fuel, and was gradually enlarged About 1879 dynamos began to be introduced into metallurgical New to 1500 h.p. ; in 1894 a factory of 5000 h.p. driven by water practice, and from that date onwards numerous schemes for utiliz1 erected at Niagara Falls. In 1890 also the Hall process this cheaper form of energy were brought before the was operated by steam power was installed at Patricroft, Lancashire, Electrical, ingfob]ic The first electrical method worthy of notice is reduction. £hat tented by Messrs E. H. and A H. Cowles in where the plant had a capacity of 300 lb per day, but by 1894 turbines of the Swiss and French works ruined the enterprise. 1885, which was worked both at Lockport, New York State and at the About 1897 the Bernard factory at St Michel passed into the hands Milton, Staffordshire. The furnace consisted of a flat rectangulai of Messrs Pechiney, the machinery soon being increased to 3000 h.p., firebrick box, packed with a layer of finely powdered charcoal and there, under the control of a firm that has been concerned inches thick. Through stuffing-boxes at the ends passed the two in the industry almost from its inception, aluminium is being electrodes, made after the fashion of arc-light carbons, and capable manufactured by the Hall process. In July 1888 the Societe of being approached together according to the reqmrcmentsofthe Metallurgique Suisse erected plant driven by a 500-h.p. turbine operation. The central space of the furnace was filled with a to carry out Heroult’s alloy process, and at the end of that year mixture of corundum, coarsely powdered charcoal, and coppei , and
