ELECTKO-METALLURGY.—ALUMINIUM. 
197 
and for the production of 1 kg. of Al. the expended energy would be 
TP = 20 electric horse-power-hours, 
equivalent to 28'8 horse-power-hours at the water-wheel. We have supposed a 
mechanical efficiency of 7 5 °/ D at the water-wheel, an electric efficiency of 88 % 
at the dynamo, and a loss of 5 °/ Q by the conductors. 
If, on the other hand, the electromotive force E = 10 volts, then the return P 
is only -0201 kg. per horse-power-hour expended in the bath, and-the energy per 
kg. of Al. is 
W = 50 electric horse-power-hours, 
or 72 horse-power-hours at the water-wheel. 
Theory therefore points to the necessity of employing currents of very great strength 
and of loio potential. The electrical manufacture of Al. accordingly demands a 
considerable motive-power : for a daily production of 200 kgs. of pure metal, 
with uninterrupted work day and night, the total energy required will be from 
700 to 800 horse-power, inclusive of the working of ventilators, crushers and 
other auxiliary machines. To produce daily 1000 kgs. of Al. would require a 
power of from 4000 to 5000 horses, which could only be obtained economically 
from' water-power. 
I extract from Ure’s “ Dictionary of the Arts 55 the following items :— 
The resistance of Al. wire to tension is between that of the best iron and best 
steel wire. 
Mr. Anderson, of Woolwich Arsenal, established that the average tenacity of 
aluminium bronze was 22'6 tons per square inch breaking weight. There was 
an elongation in one case of •009" with a weight of 4300 lbs., and in another 
case of ’034" with 3,600 lbs. 
Aluminium bronze is three times more rigid than gun-metal, and 44 times 
more rigid than brass. 
Sir Humphry Davy was the first to produce Al., probably mixed with potas¬ 
sium, in 1825 or thereabouts. 
Wohler obtained it in 1827 by reducing aluminium chloride in the form of a 
grey powder ; in 1845 he obtained globules. 
Bunsen showed in 1854 that it could be produced in reguline masses by sub¬ 
mitting the double chloride of Al. and sodium or potassium to electrolysis. 
Deville produced larger globules by following and improving on Bunsen. 
26 
