ELECTRO-METALLURGY.—ALUMINIUM. 
193 
kg. there is an expenditure of 2*15 kg. of alumina, and from 1*6 to 2 kg. of 
electric carbon, one anode only lasting 20 hours. The carbon of the latter is 
composed of crushed coke from a gas converter, pulverised in a mill, kneaded 
Fig-. 6.—Fbog-es Furnace. 
with 30 °/ D of tar, and rolled into plates about 1 metre long’, 25 centimetres 
wide and 15 centimetres thick. These are dried for four days in a stove at 300° 
Tahr., then agglomerated (a delicate operation), calcined in a reverberatory furnace 
for four or five days, and finally, when cold, sawn into two equal halves. 
The aluminium obtained has from 2 to 3 °/ Q of impurities. It is refined by 
refusion in a graphite crucible, then run out into flat ingots which, when sold, 
weigh 2’4 kg., being composed of 99 °/ 0 of pure aluminium, witt.J % -each of 
iron and silicon. 
