ELECTRO-METALLURGY.—ALUMINIUM. 
187 
double fluoride of aluminium and sodium, as a flux, a charge containing 
Double chloride.100 kg. 
Sodium . 35 „ 
Cryolite . 45 „ 
gives 10'5 kg. of aluminium. 
The Deville process was costly and complicated ; chlorine was at a high price, 
so was sodium ; much fuel was used; the furnaces, subjected to high temperatures, 
wore out rapidly ; the operations were slow and involved. Electricity has changed 
all this, and aluminium which in 1887 was worth £1 16s. per lb., now fetches 
only about 2s. 4d., and its price is likely still further to fall by the progress that 
can be foreshadowed. 
ELECTRIC PROCESSES. 
Although of recent date, these are already numerous, and may be classed under 
two principal heads. Eirst, the eledrothermic, that is utilisation of the calorific 
action of the current; the currents are at high potential, with an electromotive 
force equal to that of the voltaic arc, and never below 50 volts, and the electric 
energy appears to be entirely expended in the form of heat. Secondly, the 
elect}'olytic, where the differences of potential are much smaller, and where, if the 
scheme is really industrial, they should approximate to the minimum electromotive 
force of decomposition of the electrolytes treated. The action is comparatively 
simple, the weight of aluminium produced bears a direct ratio to the quantity of 
electricity passing through the electrolyte, whereas the electrothermic process is 
more complex, and cannot be absolutely said to involve any electrolytic action. 
The following three processes may be termed classic, for they have been put in 
practice for some years on an industrial scale. 
COWLES PROCESS.—ELECTROTHERMIC. 
Messrs. Cowles were the first to apply to the metallurgy of aluminium the 
principles of the Siemen’s electric furnace. The dissolved and reduced alumina 
with a current in the presence of carbon. The latter in combining with oxygen 
develops a quantity of heat inferior to that of the formation of alumina, and 
could therefore never have reduced that oxide without a calorific energy superior 
to that evolved by its own combustion. Messrs. Cowles, at their works in 
Cleveland, Ohio, in 1885, did not manufacture pure aluminium, but its alloys, 
the aluminium and silicon bronzes. The installation comprised a steam engine of 
125 horse-power, which actuated a dynamo producing a current of 1500 amperes 
at 50 volts. This was indeed only a field of experiment, for since 1886 there 
has been working at Lockport, near New York, the Cowles Electric Smelting 
and Aluminium Company for the manufacture of aluminium. Their works enjoy 
the use of a fall of water equivalent to 1000 horse-power, electricity is produced 
by a Brush dynamo with a current of 3000 amperes at 50 volts, and there are 18 
furnaces. 
The Cowles patents have been worked in England by the Cowles Syndicate 
Company, at Milton, near Stoke-on-Trent, since 1888. Their motive power 
consists of a horizontal compound engine of 600 nominal horse-power, and their 
electric installation comprises a large Crompton direct current dynamo with a 
power of 300 kilowatts 1 at 380 revolutions per minute. The foundry has 12 
Cowles furnaces forming two separate batteries, one for the production of 
aluminium bronze, the other of ferro-aluminium. The current is brought into 
the foundry by two aerial conductors formed of copper bars, on which circulates 
a rolling contact. To each bar is attached a lead, one going to the positive 
1 One kilowatt = 1000 watts or practical units of electrical power. 
