^^^2.] 0^ Electro-Metallurgy, 635 



was too great to permit of its use on any large scale for these 

 purposes. 



^ After Davy demonstrated, by the electrolytic extraction of potas- 

 sium and sodium, the power of the electric current to break down 

 the strong combination existing between the alkaline metals and 

 oxygen it seemed natural to expect that aluminium would also be 

 reduced by the same means. But Davy did not succeed in producing 

 any appreciable quantity of aluminium by the electrolytic method 

 iJeville and Bunsen were more successful, but they did not possess 

 the modern dynamo: that has made all the diflference, between the 

 small experimental results they achieved, and the industrial produc- 

 tion ol to-day, a production now so large that I suppose every day it 

 amounts to at least one ton, and has resulted in a very great reduction 

 ot the price of the metal. 



There are two electrolytic processes at work. One is the Hall 

 process-employed at Pittsburg, and at Patricroft, Manchester— and 

 now m experimental operation here. The other, the Herault pro- 

 cess, worked at Neuhausen, is not greatly different from the Hall 

 process—the shape of the furnace or crucible is different, and the 

 composition of the bath yielding the aluminium may be different 

 but, m all essentials these two processes are one and the same They 

 depend on the electrolysis of a fused bath, composed of cryolite 

 aluminium fluoride, fluorspar and alumina. In the Hall process this 

 mixture is contained in a carbon-lined iron crucible—the cathode in 

 an electric circuit ; and between which and the anode— a stick of 

 carbon immersed in the fused bath-a difference of potential of 10 volts 

 IS maintained. In carrying out the process on a manufacturing scale 

 there are many of these sticks of carbon to each bath. Here in our 

 experimental furnace, there is only one. ' 



. The heat developed by the passing of so large a current as we are 

 using (180 amperes), through an electrolyte of but a few inches area 

 m cross sec ion is sufficient to melt and keep red-hot the fluorides in 

 which the alumina is dissolved. 



The electrolytic action results in the separation of aluminium 

 from oxygen. The metal settles to the bottom of the pot, and is 

 tapped, or ladled out, from time to time as it accumulates. The 

 oxygen goes to the carbon cylinder, and burns it away at about the 

 same rate as that at which aluminium is produced. It is only neces- 

 sary to keep up the supply of alumina, to enable the operation to be 

 continued for a long time. I mean, of course, in addition to the 

 keeping up of the current, and the supply of carbon at the anode. 



±5y lar the greater part of the cost of aluminium obtained by 

 electrolysis, IS the cost of motive power, 20 horse-power hours 

 are expended to produce 1 lb. of aluminium. Therefore it is 

 essential for the cheap production of aluminium to have chean 

 motive power. t-iiea-p 



There is one feature about the Neuhausen production of aluminium 

 which IS very striking, and that is the generation of the SectrS 



2 u 2 



