ON THE MANUFACTURE OF ALUMINIUM. 167 



Bauxite, so called from the name of the locality where it is found in 

 France. It contains 



Silica .... 



2-8 



Titanium . 



31 



Sesquioxide of iron . 



. 25-5 



Alumina 



. 57-4 



Carbonate of lime 



0-4 



Water 



. 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 solu- 

 tion, which throws down pure alumina. The remainder of the process 

 is precisely that which is described by Mons. 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 earthern 

 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 accom- 

 panied by chloride of sodium (common salt), 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 carbonaceous matter, with a little ground 

 chalk is placed. The metallic base ot 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 

 furnace. The sodium seizes the chlorine combined with t'.ie aluminium, 

 and thus liberates the latter metal, which falls to the bottom of the 

 fused mass. 



Aluminium is used in sufficient quantity to keep the only work in 

 England — viz., that at Washington — pretty actively employed. As a 

 substance for works of art, when whitened by means of hydrofluoric 

 and phosphoric acid, it appears well adapted, as it runs into the most 

 complicated patterns, and has the advantage of preserving its colour, 

 from the absence of all tendency to unite with sulphur, or to become 

 affected by sulphuretted hydrogen, as happens with silver. 



A large amount of the increased activity in the manufacture referred 

 to, is due to the exceeding beauty of the compound with copper, already 

 spoken of, which is so like gold as scarcely to be distinguishable from 

 that metal, while it possesses the additional valuable property of being 

 nearly as hard as iron. 



