TRANSACTIONS OF THE SECTIONS, 33 
researches bestowed upon the process by the distinguished chemist, M. St. Claire 
Deville, of Paris. Upon the introduction of its manufacture at Washington, three 
and a half years ago, the source of the alumina was the ordinary ammonia-alum 
of commerce (a nearly pure sulphate of alumina and ammonia). Exposure to heat 
drove off the water, sulphuric acid, and ammonia, leaving the alumina behind, 
This was converted into the double chloride of aluminium and sodium by the pro- 
cess described by the French chemist, and practised in France, and the double 
chloride was subsequently decomposed by fusion with sodium. Faint, however, as 
the traces might be of impurity in the alum itself, they to a great extent, if not 
entirely (being of a fixed character when exposed to heat), were to be found in the 
alumina. From the alumina, by the action of chlorine on a heated mixture con-. 
sisting of this earth, common salt, and charcoal, these impurities, or a large propor- 
tion thereof, found their way into the sublimed double chloride, and, once there, it 
is unnecessary to say that, under the influence of the sodium in the process of re= 
duction, any silica, iron, or phosphorus found their way into the aluminium sought 
to be obtained. Now it happens that the presence of foreign matters, in a degree 
so small as almost to be infinitesimal, interferes so largely with the colour as well 
as with the malleability of the aluminium, that the use of any substance containing 
them is of a fatal character. Nor is this all, for the nature of that compound 
which hitherto has constituted the most important application of this metal— 
aluminium-bronze—is so completely changed by using aluminium containing 
the impurities referred to, that it ceases to possess any of those properties which 
render it valuable. As an example of the amount of interference exercised by very. 
minute quantities of impurity, it is perhaps worthy of notice that very few varieties 
of copper have been found susceptible of being employed for the manufacture of 
aluminium-bronze ; and hitherto the author has not, nor have they in France, been 
able to establish in what the difference consists between copper fit for the produc- 
tion of aluminium-bronze and that which is utterly unsuitable for the purpose. 
These considerations have led us, both here and in France, to adopt the use of an= 
other raw material for the production of aluminium, which either does not contain 
the impurities referred to as so prejudicial, or contains them in such a form as to 
admit of their easy separation. This material is Bauxite, so called from the name 
of the locality where it is found in France. It contains 
Silica 244 SOR Aes 0 Bh 2°8 
Wirtamium if 26520. 03..18 RSs. eel 6.2 hs, 0 ne eR 31 
Sesquioxidevofiron).!.. 1%. 2A NR ee ee 25'5 
AMuiminat 252 00, 52.0..C08)..18. SR eee 57-4 
Carbonate Of JIMS; } «,..«:cheisve.ocasateey eee 0:4 
SW BEGI.. 6.c ace sio.$.c,clsbave febdlace aoa ogacate eS 10-8 
100-0 
The bauxite is ground and mixed with the ordinary soda-ash of commerce, and 
then heated in a furnace. The soda combines with the alumina, and the aluminate 
of soda so formed is separated from the insoluble portions, viz. peroxide of iron,. 
silico-aluminate of soda, &c., by lixiviation. Muriatic acid or carbonic acid is then 
added to the solution, which throws down pure alumina. The remainder of 
the process is precisely that which is described by M. St. Claire Deville. The, 
alumina is mixed with common salt and charcoal, made into balls the size of an 
orange, and dried. These balls are placed in vertical earthen retorts, kept at a red 
heat, and through the heated contents chlorine gas is passed. The elements of the, 
earth, under the joint influence of carbon and chlorine at that temperature, are: 
separated—the carbon taking the oxygen, and the chlorine the aluminium. — This- 
latter substance, accompanied by chloride of sodium, sublimes over, and is collected,: 
as a double chloride of aluminium and sodium. In small iron retorts, kept at as 
high a temperature as iron can bear, a mixture of soda (carbonate of soda) and carbo=. 
naceous matter, with a little ground chalk, is placed. The metallic base of the alkali: 
distils over and is collected in coal oil. A portion of the double chloride and sodium,- 
along with fluxes, is exposed to a full red heat in a reverberatory fummage. The 
1863. ; : 
