chloride, MgCl2, by the battery. Deville's account of the process is as follows:-*

"It appears to me impossible to obtain aluminium by the battery in aqueous solutions. I should believe this to be an impossibility if the brilliant experiments of Mr. Bunsen in the preparation of barium did not shake my convictions. Still I must say that all the processes of this description which have recently been published for the preparation of aluminium bave failed to give me good results. To prepare the bath for decomposition in the dry way, I heated a mixture of 2 parts A12C16 and 1 part NaCl, dry and pulverized, to about 200° in a porcelain capsule. They combine with disengagement of heat, and the resulting bath is very fluid. The apparatus which I use for the decomposition comprises a glazed porcelain crucible, which as a precaution is placed inside a larger one of clay. The whole is covered by a porcelain cover pierced by a slit to give passage to a large, thick leaf of platinum, which serves as the negative electrode; the lid has also a hole through which is introduced, fitting closely, a well-dried porous cylinder, the bottom of which is kept at some distance from the inside of the porcelain crucible. This porous vessel incloses a pencil of retort carbon, which serves as the positive electrode. Melted Al2C16.2NaCl is poured into the porous jar and into the crucible so as to stand at the same

* Ann. de Chem. et de Phys. [3], 46, 452.

height in both vessels; the whole is heated just enough to keep the bath in fusion, and there is passed through it the current from several Bunsen cells, two cells being strictly sufficient. The annexed diagram shows the crucibles in section.

Fig. 15.

"The aluminium deposits with some NaCl on

the platinum leaf; the chlorine, with a little Al2C1, is disengaged in the porous jar, and forms white fumes, which are prevented from rising by throwing into the jar from time to time some dry,

pulverized NaCl. To collect the aluminium, the platinum leaf is removed when sufficiently charged with the saline and metallic deposit; after letting it cool the deposit is rubbed off and the leaf placed in its former position. The material thus detached, melted in a porcelain crucible, and after cooling washed with water, yields a gray, metallic powder, which is melted under a layer of AlC16.2NaCl and reunited into a button."

Bunsen* adopted a similar arrangement. The porcelain crucible containing the bath of AlC1®. 2NaCl kept in fusion was divided into two compartments in its upper part by a partition, in order to separate the chlorine liberated from the aluminium reduced. He made the two electrodes of retort carbon. To reunite the pulverulent aluminium, Bunsen melted it in a bath of Al2C16.2NaCl, continually throwing in enough NaCl to keep the temperature of the bath about the fusing point of silver.

Deville,† without being acquainted with Bunsen's investigations, employed the same arrangement, but he abandoned it because the retort carbon slowly disintegrated in the bath, and a considerable quantity of Al2C16.2NaCl was lost by the higher heat necessary to reunite the globules of aluminium after the electrolysis. Deville also

observed that by working at a higher temperature, as Bunsen has done, he obtained purer metal, but in less quantity. The effect of the high heat is that silicon chloride is formed and volatilizes, and the iron which would have been reduced with the aluminium is transformed to FeCl2 by the A12C16, and thus the aluminium is purified of silicon and iron.

Mierzinski makes the following practical remarks on the use of electricity in producing aluminium :"An important factor which we must notice in the present production of aluminium is the application of electricity. On all sides the greatest efforts are being made to apply electricity to chemical technology; in the future the importance of electricity will centre on its application to reducing metals. Even in the year 1807 Davy succeeded in decomposing caustic potash by means of a current from a 400 element Wollaston battery. But we now have magneto-electric and dynamo-electric machines which are much lighter and cheaper than they were in Davy's time. The application of electricity for producing metals also possesses the advantage not to be ignored, that a degree of heat may be attained with it such as cannot be reached by a blowpipe or regenerative gas furnace. The highest furnace temperature attainable is 2500 to 2800° C., but long before this point is reached the combustion becomes so languid that the loss of heat by radiation almost equals the production of

heat by combustion, and hinders a further elevation of temperature. But in applying electricity, the degree of heat attainable is theoretically unlimited. A further advantage is that the smelting takes place in a perfectly neutral atmosphere, the whole operation goes on without much preparation and under the eyes of the operator. Finally, in ordinary furnaces the refractory material of the vessel must stand a higher heat than the substance in it, whereas by smelting in an electrical furnace the material to be fused has a higher temperature than the crucible itself.

"The manufacture of aluminium is effected now either by separating out the metal itself directly from the solutions of its salts or by reducing it with sodium. However, in spite of numerous attempts, sodium has not been replaced as a reducing agent. In the production of aluminium, the making of A1203 from beauxite costs 9.7 per cent., making the APC16.2NaCl 33.4 per cent., and decomposing by sodium 56.9 per cent. of the whole cost. The attempt to reduce alumina directly by carbon Mr. W. Weldon considers as impossible because he could not produce the temperature required for the reaction to take place. Hence appears the great importance of utilizing the temperature attainable by the electric current. The separation of aluminium by electrolysis is now done only by the use of anhydrous Al2Clo.2NaCl, melting at 200° C. The anodes are made of plates