Oct. 1 8, 1888] 



NA TURE 



593 



The first practical steps for the manufacture of alu- 

 minium were taken in France, following the discoveries 

 of W older and of Deville, and that country has retained 

 the monopoly of its production up to the present time. 

 Aluminium was first obtained in a pure state in the 

 year 1854 by St. Claire Deville whilst working in the 

 laboratory of the Normal School, Paris, with a totally 

 different object. Some pounds of this metal which were 

 shown at the Paris Exhibition of 1855 had been made at 

 the chemical works of Javel ; subsequently larger plant 

 was put up at some works at Glaciere ; later on we find 

 the manufacture in an improved form transferred to 

 Nanterre ; and soon afterwards it was removed to the 

 position in which it has ever since remained, viz. at 

 Salindres, at the works at that time belonging to Messrs 

 Merle and Co., but now carried on by Messrs. Pechiney 

 and Co. 



Shortly after Deville obtained aluminium by reducing 

 the chloride with sodium, he also succeeded in isolating 

 it by electrolyzing the double chloride of aluminium 

 and sodium in a state of fusion. Many attempts have 

 been made to improve this method, but although within 

 the last year or two works have been put up both in 

 Germany and in France which are stated to be able to 

 produce aluminium at a comparatively cheap rate, there 

 is no trustworthy evidence to show that they can compete 

 with the sodium process. On the face of it there appears 

 no reason why aluminium should not be economically 

 manufactured in this way, since it is an undoubted fact 

 that it can be done in the case of magnesium. There 

 are, however, difficulties in getting aluminium to de- 

 posit in a satisfactory condition which do not occur with 

 magnesium. 



Recently, by applying electricity in a totally different 

 way, alloys of aluminium have been manufactured on a 

 comparatively large scale in America by Messrs. Cowles 

 Bros. Works for the purpose are also being opened by 

 them in England. This process, it will be remembered, 

 consists in passing a powerful current between two carbon 

 electrodes embedded in a mixture of alumina, charcoal, 

 and the other metal required for the alloy. By this pro- 

 cess aluminium in an unalloyed form has not yet been 

 obtained, at any rate commercially. 



Some fourteen years ago, Messrs. Bell Bros., of New- 

 castle-on-Tyne, erected works to manufacture aluminium 

 by means of sodium ; but, after incurring great expense, 

 they abandoned the attempt, partly owing to difficulties 

 experienced in obtaining it sufficiently pure for the manu- 

 facture of alloys, and partly because they were unsuccess- 

 ful in getting it used on a sufficiently large scale. Another 

 factory put up in Berlin was similarly abandoned, almost 

 as soon as erected. 



In America, a few years ago, Colonel Frismuth sold 

 aluminium, which, he stated, was made by an improved 

 sodium process of his invention ; he did not, however, 

 reduce the price, and his claims have not been substan- 

 tiated. The same thing may be said of the Aluminium 

 Company which was started about the same time in this 

 country to work the patents of Mr. Webster, of Birm- 

 ingham. It is, however, by this Company, after having 

 undergone reconstruction, that the process is now being 

 worked which warrants our opening statement that ;i 

 fresh epoch has been reached in the manufacture of 

 aluminium. 



The process in question is the outcome of experiments 

 commenced some six or seven years ago by Mr. H. Y. 

 Castner in New York. He appears to have come to the 

 conclusion that aluminium could only be satisfactorily pro- 

 duced by means of sodium, and he accordingly commenced 

 work to try and improve and cheapen the manufacture 

 of sodium. Having obtained what he considered suf- 

 ficiently satisfactory results, he came over to this country 

 about two years ago, and erected experimental works at 

 Lambeth, where, after further trials, he succeeded in de- 



monstrating that he was really able to produce sodium 

 at a much cheaper rate than had before been possible ; 

 in fact, it appears he is able to produce sodium at less 

 than is. a pound, whereas it had previously cost about 4^. 

 This success led to the erection of works at Oldbury, 

 which have been recently completed, and are now in 

 successful operation. 



In the process hitherto employed to produce sodium, an 

 intimate mixture of carbonate of soda, lime, and charcoal 

 is first calcined at a red heat, and this having been trans- 

 ferred to small wrought-iron cylinders (mercury-bottles or 

 large gas-piping being commonly used), it is heated to 

 about 1500° C, when the metal, having become reduced 

 to the metallic state, distils over, and is condensed in a 

 fiat iron mould. In practice, this method is found to be 

 defective both mechanically and chemically. 



At least half the ultimate cost of production results 

 from the wear and tear of the furnace, and the destruc- 

 tion of the retorts or cylinders by the comparatively high 

 temperature. Looking at it from the chemical point of view, 

 we find the condition of things almost as bad; little, if 

 any, more than 40 per cent, of the sodium actually in 

 the charge being obtained in the metallic state. 



All these difficulties arise from the presence of lime in 

 the charge, the lime being added to stiffen the mixture, 

 and so prevent the charcoal from separating from the 

 soda. But the thickening of the charge, which for one 

 reason is so desirable, is equally objectionable for others. 

 It is the thickening of the charge which necessitates 

 the use of small cylinders and a high temperature : the 

 material being a bad conductor, it could not otherwise be 

 sufficiently heated. Another important difficulty in the 

 old process arose from the presence of carbonic oxide in 

 the gases produced in the reactions. Sodium vapour, 

 when near its condensing-point, reacts upon carbonic 

 oxide, forming a black refractory material which is 

 exceedingly explosive. This is particularly the case 

 with potassium, and is the principal reason why potassium 

 is so much dearer than sodium. 



Mr. Castner originated the idea of weighting the par- 

 ticles of carbon, thus doing away with the necessity of 

 adding lime. The practical results of this modification 

 in the method of manufacturing sodium are very far- 

 reaching and important. The charge being perfectly 

 fluid, it is no longer necessary to employ such a high 

 temperature, since there is a continuous circulation of 

 fresh material to the sides of the crucible, where the 

 temperature is sufficiently high to set up the reactions by 

 which the sodium is reduced to the metallic state. For 

 the same reason large crucibles can be used instead of 

 small cylinders. Also, the temperature of the operation 

 being reduced from about 1400" C. to about 800' C, cast 

 iron or cast steel may be used for the containing vessels 

 instead of wrought iron. 



The carbon particles are weighted by means of iron. 

 The iron is first obtained in a fine state of division by 

 reducing oxide of iron — "purple ore" being generally 

 used for the purpose — in " producer gas," a mixture of 

 carbonic oxide and hydrogen. The finely-divided iron 

 thus obtained is stirred into molten pitch, which is then 

 cooled and broken up into lumps. The next operation 

 consists in heating these lumps in crucibles, whereby a 

 coke is produced containing carbon and iron in the pro- 

 portion of about 30 : 70 ; this material, technically called 

 "carbide," having been ground up very fine, is incor- 

 porated with certain proportions of caustic soda and car- 

 bonate of soda, and the mixture is charged into large 

 crucibles, where it is heated until the violent effervescence, 

 due to the escape of carbonic acid and hydrogen, which 

 takes place at first, has subsided. These crucibles are 

 provided with holes at the bottom, closed by movable 

 plugs. When the effervescence has ceased, the charge, 

 in a liquid state, is run out into smaller crucibles and 

 transferred to the furnace in which the distillation of the 



