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ELECTRO-METALLURGY.—ALUMINIUM. 
This pure aluminium, added to 6 % °f copper, makes an alloy of greater 
tensile strength than itself. 
The manufacture of aluminium bronzes and brasses has now lost its importance 
and will probably soon cease. 
Aluminium is coming more and more into use in metallurgy : it is pre¬ 
eminently the reducing agent; the heat required for the production of alumina 
being according to M. Berthelot’s principle of maximum work, more considerable 
than for other metallic oxides, these in their re-actions will cede their oxygen to 
aluminium. The latter replaces advantageously silicon and manganese in the 
refining of steel and the manufacture of flawless cast-steel. It also plays the 
part of phosphorous in bronze foundries, and in the metallurgy of nickel. 
MINET PROCESS. 
This is a true example of the electrolytic process by igneous fusion. In 
October, 1891, M. A. Minet, after trials at other places, started an aluminium 
factory at Calypso, two kilometres from St. Michel-de-Maurienne, in Savoy. The 
motive power is furnished by the torrent of the Valloirette which descends from 
the Gabbier and falls into the Arc at Saint-Michel. The water is taken at 133 
metres above the factory, and reaches the water-chamber by a masonry canal partly 
hollowed out as a tunnel. Two tubes lead from the water-chamber at a slope of 
45° delivering water to the water-wheels at the rate of 3|- cubic metres, or 9436 
gallons a second, giving 4000 horse-power. There are two Hillairet direct-action 
dynamos of 300 and 400 kilowatts respectively. Deville foresaw the industrial 
production of aluminium by electrolysis, and pointed out cryolite 1 as susceptible 
of decomposition. He tried it with a bath composed of 
Double aluminium and sodium chloride ... 2 
Sodium chloride . 1 
heated to 200° Cent., but in his time the use of electricity would have been too 
costly as the basis of an industrial process. Minet has resumed Deville’s experi¬ 
ments and studied the electrolysis of the Al. salts, particularly the chloride and 
fluoride. The latter is difficult to fuse, its point of volatilisation being very near 
its point of fusion, and it is the same with the chloride, only at a lower tempera¬ 
ture. The simple salts have therefore been discarded, and double ones have been 
tried, with a radical more electro-positive than Al., and which would not be set 
at liberty before it, sodium for instance. A bath of 
Double Al. and sodium fluoride . ... 35 
Sodium chloride . 65 
has accordingly been adopted. It is sufficiently fluid at 800° Cent., and is 
scarcely volatile at 1100° Cent. Its electric conductivity in terms of its tem¬ 
perature is given by the formula :— 
C t = 3-1 ^1 + '0022 (t - 870°) J 
As the apparatus given in Eig. 7 was not continuous in its action, the system 
was so arranged (Eig. 8) that the cast-iron trough itself forms the kathode, its 
interior being lined with conducting carbon. 10 to 12 kg. of metal are run out 
at a time; the strength of the current is 3600 amperes ; a trough lasts about a 
month; 1 kg. of Al. requires 3 kg. of alumina; the metal obtained by the first 
fusion is re-melted and refined in a crucible. The important conditions for 
steady work are uniformity in the composition of the bath and of the current’s 
strength. The dimensions of the electrodes should be therefore in direct ratio to 
1 Cryolite is the double aluminium and aodium fluoride and is found chiefly in Greenland. (6 
Na F, Alg F 6 ).— F.E,B.L, 
