ALITMINIUM 127 



in effecting the reduction of the chlorides by any of the common metals. He ad- 

 hered to Wohler's and Bunsen's methods, carrying them out on a larger scale, -with 

 modifications and improvements in the details, which enabled him to obtain the metal 

 in such quantities, and thus to study its properties with so much success, as to suggest 

 numerous applications, the probability of which never entered the minds of the ori- 

 ginal discoverers. Very great credit is therefore due to M. Dovillo, although it is the 

 practice amongst the German chemists to detract from, or even deny, his merit 



The following is the method described by M. Deville for the preparation of this 

 interesting metal : 



Having obtained the chloride of aluminium, ho introduces into a wide glass 

 for porcelain) tube 200 or 300 grammes of this salt between two plugs of asbestos 

 (or in a boat of porcelain or even copper), allows a current of hydrogen to pass 

 from the generator through a desiccating bottle containing sulphuric acid and 

 tubes containing chloride of calcium, and finally through the tube containing the 

 chloride ; at the same time applying a gentle heat to the chloride, to drive off any free 

 hydrochloric acid which might be formed by the action of the air upon it. He now 

 introduces at the other extremity of the tube a porcelain boat containing sodium ; and 

 when the sodium is fused the chloride of aluminium is heated, until its vapour comes 

 in contact with the fused sodium. A powerful reaction ensues, considerable heat is 

 evolved, and by continuing to pass the vapour of the chloride over the sodium until 

 the latter is all consumed, a mass is obtained in the boat of the double chloride of 

 aluminium and sodium NaCl, AF Cl* (2Na.Cl, A1 7 C1 6 ), in which globules of the 

 newly-reduced metal are suspended. It is allowed to cool in the hydrogen, and 

 then the mass is treated with water, in which the double chloride is soluble, the 

 globules of metal being unacted upon. 



These small globules are finally fused together in a porcelain crucible, by heating 

 them strongly under the fused double chloride of aluminium and sodium, or even 

 under common salt. 



This process, which succeeds without much difficulty on a small scale, is performed 

 far more successfully as a manufacturing operation. Two cast-iron cylinders are 

 now employed instead of the glass or porcelain tube, the anterior one of which 

 contains the chloride of aluminium, whilst in the posterior one is placed the sodium 

 in a tray, about 10 Ibs. being employed in a single operation. A smaller iron 

 cylinder intermediate between the two former is filled with scraps of iron, which 

 serve to separate iron from the vapour of chloride of aluminium, by converting the 

 perchloride of iron into the much less volatile protochlorido. They also separate 

 free hydrochloric acid and chloride of sulphur. 



During the progress of the operation the connecting tube is kept at a temperature 

 of about 400 to 600 F. ; but both the cylinders are but very gently heated, since the 

 chloride of aluminium is volatile at a comparatively low temperature, and the reaction 

 between it and the sodium when once commenced generates so much heat that 

 frequently no external aid is required. 



Preparation of Aluminium by Electrolysis. 'Mr. Gore has succeeded in obtaining 

 plates of copper coated with aluminium by the electrolysis of solutions of chloride of 

 aluminium, acetate of alumina, and even common alum ; ' but the unalloyed metal 

 cannot be obtained by the electrolysis of solutions. Deville, however, produced it in 

 considerable quantities by the method originally suggested by Bunsen, viz. by the 

 electrolysis of the fused double chloride of aluminium and sodium Na Cl, AP Cl s 

 (ZTTaCl. A1*C1 8 ); but since this process is far more troublesome and expensive than 

 its reduction by sodium, it has been altogether superseded. 



Preparation of Aluminium from Cryolite. So early as March 30, 1855, a specimen of 

 aluminium was exhibited at one of the Friday-evening meetings of the Eoyal Institu- 

 tion, which had been obtained in Dr. Percy's laboratory by Mr. Allan Dick, by a 

 process entirely different from that of Deville, which promised, on account of its great 

 simplicity, to supersede all others.* It consisted in heating small pieces of sodium, 

 placed in alternate layers with powdered cryolite, a mineral now found in consider- 

 able abundance in Greenland, which is a double fluoride of aluminium and sodium, 

 analogous to the double chloride of aluminium and sodium, its formula being 3Na F, 

 Al* F* (6XTa F. JBU 2 P 8 ). The process has the advantage that one of the materials 

 is furnished ready formed by nature. 



The experiment was only performed on a small scale by Mr. Dick in a platinum 

 crucible lined with magnesia; the small globules of motel, which were obtained at 

 the bottom of the mass of fused salt, being subsequently fused together under chloride 

 of potassium or common salt. 



Before the description of these experiments was published, M. Kose, of Berlin, 



' PflH. Mag. vil. 207. ' Ibid. x. 364. 



