128 ALUMINIUM 



published a paper in September, 1855, on tho samo subject. 1 In Rose's experiment* 

 be employed cast-iron crucibles, in which was heated ten parts of a mixture of equal 

 weights of cryolite and chloride of potassium with 2 parts of sodium. The aluminium 

 was obtained in small globules, which were fused together under chloride of potassium, 

 as in Mr. Dick's experiments. 



Hose experienced a slight loss of aluminium by fusion under chloride of potassium, 

 and found it more advantageous to perform this fusion under a stratum of tho double 

 chloride of aluminium and sodium, as Deville had done. 



He never succeeded in extracting the whole quantity of aluminium present in tho 

 cryolite (13 per cent.), chiefly on account of tho ready oxidisability of tho metal 

 when existing in a very finely divided state, as some of it invariably does. 



It does not appear that any attempt has since been made to obtain aluminium on 

 the largo scale from cryolite, probably from the supply of the mineral not proving so 

 abundant as was at one time anticipated. 



In all tho processes which have been found practicable on any considerable scale, 

 for the manufacture of aluminium, the powerful affinities of sodium are employed for 

 the purpose of eliminating it from its compounds. The problem of the diminution of 

 the price of aluminium therefore resolves itself into the improvement of the methods 

 for procuring sodium, so as to diminish the cost of the latter metal. M. Devillo's 

 attention was therefore directed, in the early steps of tho inquiry, to this point ; and 

 very considerable improvements have been made by him, which will be found fully 

 described under the head of SODIUM.. 



Deville' has since suggested the employment at once of tho double salt of chloride 

 of aluminium and chloride of sodium (NaCl, Al 2 Cl 1 ), instead of tho simple chloride 

 of aluminium, so as to obtain the metal by means of sodium. Ho uses 400 parts 

 of this double salt, 200 of common salt, 200 of fluor spar, and 7o to 80 of sodium. 

 The above-mentioned salts are dried, powdered, and mixed together ; then with these 

 the sodium, in small pieces, is mixed, and the whole heated in a crucible under a 

 layer of common salt. After the reaction is complete, the heat is raised so as to pro- 

 mote the separation of the aluminium in the form of a button. It was found, however, 

 tliat cryolite was, with advantage, substituted for the fluor spar. 



C. Brunner s employs artificially prepared fluoride of aluminium ; but this method 

 cannot offer any advantage over the employment of the chloride, which is cheaper, or 

 the cryolite, which nature affords. 



The following remarks on the manufacture of aluminium are from the pen of Mr. 

 Isaac Lowthian Bell of Newcastle, at whose works at Washington this metal was, 

 until lately, produced : 



Upon the introduction of its manufacture at Washington, 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, those 

 impurities, or a large proportion thereof, found their way into the sublimed double 

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

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

 into tho aluminium 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 containing them is of a fatal character. Nor is this all, for tho 

 nature of that compound which hitherto has constituted tho most important applica- 

 tion 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 quantities 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 wo 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 usually unsuitable for 

 the purpose. Those considerations have led us, both hero and in France, to adopt 

 tho use of another raw material for the production of aluminium, which either .does 



Poggondorff's Annalon, and Phil. Mag. x. 233. Ann. de Chlm. et Phys. xlvi. 415. 



* Chemical Gazette,.1856, 388. 



