ELECTRO-METALLURGY.—ALUMINIUM. 
191 
of the crucible was confined to the space lying between the electrodes. Outside 
of that the temperature was lower, and the dissolved elements recombined. To 
obviate this he makes the anode move backwards and forwards mechanically, 
while the vat containing the bath is made to turn round a vertical axis. The 
anode is made of plates of carbon dust prepared in a retort, compressed and 
consolidated with tar, and the kathode of a block of copper under a layer of 
agglomerated graphite. Cryolite in powder, which easily melts, is employed in¬ 
stead of copper to start the arc, and pure alumina is gradually introduced while 
the former melts, and the charge is further fed, not only with alumina, but with 
aluminium fluoride ; the electromotive force is from 20 to 25 volts. Neuhausen 
now enjoys the above improvements of Kiliani together with the fixed crucible as 
kathode of Heroult. Tigs. 3 and 4 show the type of furnace employed, consist- 
Fig. 3.— Neuhausen Fuenace. 
Elevation. 
Fig. 4.—Neuhausen Fuenace. 
Plan. 
ing of a block of compressed carbon enclosed in iron plates, as kathode; the 
current, brought by non-insulated copper cables, comes through terminals screwed 
into the plates ; at the bottom of the crucible is a running-out passage, closed 
by a carbon plug which is held up by an external spring. The cover of the bath 
