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ON THE MANUFACTURE OF ALUMINIUM. 



BY ISAAC LOWTHIAN BELL. 



The progress of the manufacture of this — so far as the arts are con- 

 cerned — new metal has scarcely been such as to require much to be 

 added to those admirable researches bestowed upon the process by the 

 distinguished chemist, M. St. Claire Deville, of Paris. Upon the intro- 

 duction of its manufacture at Washington, three and a half years ago, 

 the source of the alumina was the ordinary ammonia alum of commerce 

 — a nearly pure sulphate of alumina and ammonia. Exposure to heat 

 drove off the water, sulphuric acid, and ammonia, leaving the alumina 

 behind. This was converted into the double chloride of aluminium and 

 sodium by the process described by the French chemist and practised 

 in France, and the double chloride was subsequently decomposed by 

 fusion with sodium. Faint, however, as the traces might be of impurity 

 in the alum itself, they to a great extent, if not entirely (being of a fixed 

 character when exposed to heat) were to be found in the alumina. From 

 the alumina, by the action of chlorine on a heated mixture consisting 

 of this earth, common salt and charcoal, these impurities, or a large pro- 

 portion thereof, found their way into the sublimed double chloride, 

 and, once there, it is unnecessary to say that, under the influence of the 

 sodium in the process of reduction, any silica, iron, or phosphorus found 

 their way into the ahmiinium sought to be obtained. Now, it happens, 

 that the presence of foreign matters, in a degree so small as almost to 

 be infinitesimal, interferes so largely with the colour, as well as with 

 the malleability of the aluminium, that the use of any substance con- 

 taining them is of a fatal character. Nor is this all, for the nature of 

 that compound which hitherto has constituted the most important 

 application of this metal — aluminium-bronze — is so completely changed 

 by using aluminium containing the* impurities referred to that it ceases 

 to possess any of those properties which render it valuable. As an 

 example of the amount of interference exercised by very minute quan- 

 tities of impurity, it is perhaps worthy of notice that very few varieties 

 of copper have been found susceptible of being employed for the manu- 

 facture of aluminium-bronze ; and hitherto we have not at Washington, 

 nor have they in France, been able to establish in what the difference 

 consists between copper fit for the production of aluminium-bronze, and 

 that which is utterly unsuitable for the purpose. These considerations 

 have led us, both here and in France, to adopt the use of another raw 

 material for the production of aluminium, which either does not con- 

 tain the impurities referred to as so prejudicial, or contains them in 

 such a form as to admit of their easy separation. This material is 



