THE ELECTEIC FURNACE. 



299 



Ahuuiniviin Company, of Foj^ers, New Brunswick, and ono or two 

 metallurgical tirms on the Continent. 



It consists of an outer iron casing- or container F (tig. 4) resting on 

 an insulating base. This container is lined with massive car}»on plates, 

 cemented together with tar or suita})le conducting material, and so 

 arranged as to form at the center a recess or liearth H, an outlet o^ 

 from the ]H)ttom leading out to the exterior of the furnace, and pro- 

 viding for drawing off the molten metal. 

 ^ A series of copper pins e (\ di'iven into the iron walls of the container, 

 ""serve as a means of terminal connection to the car])on ])locks, which 

 constitute one electrode of tlie furnace, while the other, C, consists of 

 a number of carbon plates, placed face to face, like the leaves of a 

 book, the spaces between being tilled in with some good electrical con- 

 ductor, such as sheet copper. The composite electrode thus built up 

 is mounted in a frame E, by means of whicli it can ])e raised or low- 

 ered as required, and terminal con- 

 nection is secured by means of an 

 encircling clamp T. The electrode C 

 passes through a clearance opening 

 in the lid L of the furnace, which 

 consists of graphite plates; openings 

 'p J) are also provided for the intro- 

 duction of the raw material (alumina 

 and cryolite), thereby making the 

 furnace continuous in operation. 



The furnace is charged with pui'i- 

 fied alumina and cryolite, as already 

 indicated, and, the electrode C having 

 been lowered, the action is started. The heat thus set up, combined 

 with the electrolytic action of the current, results in the setting free 

 of metallic aluminum, while oxygen gas is evolved at the positive or 

 carl)on electrode and enters into coml)ination with it, forming the gases 

 monoxide and dioxide of carbon. 



The molten aluminum collects at the l)ottom of the hearth and is 

 tapped off through the outlet o, fresh material being fed in and the 

 height of the electrode C regulated as the operation proceeds. 



The King furnace is also of the arc variety and is utilized in the 

 manufa<'ture of carbide in ingot form. It consists of a tire-brick 

 cham))er, through the roof of which passes vertically the upper 

 adjustable electrode. The lower, ffxed, electrode is carried l)y a small 

 truck or trolley, which runs along rails at the ])ase of the structure and 

 acts the part of crucil)le or hearth. The lime and carbon are fed into 

 it down lateral. channels in the walls of the furnace and are caused to 

 coml)ine by the heat of the arc set up. Th(> upper (dectrode is gradu- 

 ally raised as the raw material is fed in, until, at a certain point, the 



Fig. 4. 



