288 ANNUAL OF SCIENTIFIC DISCOVERT. 



In the manufacture of sodium the carbon is now replaced by coal. De- 

 ville uses a coal which burns with considerable flame. It is important that 

 the mixture should be well dried before subjected to decomposition. The 

 proportion used are as follows : 



Carbonate of soda, 30 kit. 



Coal, 13 " 



Chalk, 5 " 



The soda ought to be from the crystallized carbonate ; the soda of the 

 shops gives bad results without Deville's knowing precisely why. 



Mr. Newton (for a foreign correspondent) has also patented in England, a 

 process by which the production of aluminium is reduced to an essentially 

 practical and commercial form. It has hitherto been the practice to effect 

 the reduction of aluminium from its different compounds (single or double 

 chlorides or fluorides) in closed vessels, and in published descriptions on 

 this subject it has been usual to mention the employment of crucibles en- 

 closed in tubes or retorts of fire-clay, coated with alumina. As the em- 

 ployment of the apparatus is attended with disadvantages, the inventors 

 have, in the first place, substituted for such apparatus vessels made of cast 

 or wrought iron, of varying form but generally approaching that of cruci- 

 bles, pots, or seggars, in which vessels, the reaction is effected in the same 

 manner as in vessels of clay. The inventors of the present improvements 

 have also succeeded in effecting the reduction in chambers made of brick- 

 work or fire-clay, which may be either heated in the same manner as a 

 reverberatory furnace, or by the transmission of heat through the sides. 

 The apparatus employed by preference, however, is a reverberatory furnace, 

 the bed of which, having a portion of it inclined, is arranged in a suitable 

 manner for facilitating the collection of the metal as it is produced ; but the 

 furnaces ordinarily employed for the manufacture of soda may be used for 

 this purpose. Another improvement consists in modifying the composition 

 of the mixture or matters for effecting the reaction in such a manner as to 

 ensure successful operation, even when operating upon small quantities of 

 materials, or with vessels of small capacity, such as clay retorts or other 

 closed vessels. This is effected by wholly, or to a great extent, dispensing 

 with the marine salt, which is usually added either to the simple chloride of 

 aluminium, the double chloride of aluminium and sodium, or to the fluoride 

 of aluminium and sodium (cryolite), and in simply adding a suitable pro- 

 portion of fluoride of calcium. The use of marine salt had been hitherto 

 considered necessary for the successful performance of the reduction, and in- 

 dispensable as a flux for causing the metal to unite ; in operating with the 

 double chloride of aluminium and of sodium it had been pointed out, and 

 always employed in the proportion of fifty per cent, to the double chloride. 

 It has been found by experience that by diminishing this proportion better 

 results are obtained, and by dispensing with the marine salt altogether, the 

 largest quantity of metal is obtained. The following is the mode of operat- 

 ing, according to this improvement, when it is required to effect the reduc- 

 tion of the double chloride : Take of the double chloride of aluminium and 



