Aluminium. 179 



be formed, should unite with some of the undecomposed oxide 

 — which does not seem to occur, though aluminates of the 

 alkalies are very easily made. But M. Chapelle, in 1854, pro- 

 cured it by introducing pulverized clay, sea salt, and powdered 

 charcoal, into a common crucible, and heating the mixture with 

 coke, though not to whiteness, in a reverberatory furnace. 

 When the crucible was cold, a considerable quantity of minute 

 globules of aluminium were found at the bottom. It must be 

 admitted that the simplicity of this method, if it could be 

 rendered economical, would make it deserving of preference : 

 and it is not improbable that it may hereafter be so improved 

 as to supersede all others. To obtain aluminium through the 

 medium of a troublesome metal, seems at best a clumsy process. 

 It is, however, the most successful that has been yet devised ; 

 and we are indebted for it, in its present improved state, to 

 the ingenuity and researches of Deville, whose method is a 

 modification of Wohler's. He received from the present 

 Emperor Napoleon the funds necessary for making his ex- 

 periments on a large scale, and in a satisfactory manner : and 

 he first published an account of them in 1854. 



It occurred to him that, on account of its smaller equivalent, 

 and the commercial value of its salts, sodium would be better 

 for the purpose of obtaining aluminium than potassium, which 

 had been employed by Wohler. Other advantages, besides, 

 were found to follow from its adoption : the manufacture 

 of sodium is easier, and even safer, than that of potassium : 

 and when the process goes on well, those carbon compounds 

 which are so annoying with potassium, do not make their 

 appearance : nor is its reduction accompanied by the explosive 

 substances — probably compounds of hydrogen — which are so 

 dangerous in the reduction of potassium. Moreover, the use 

 of potassium in obtaining aluminium is not very safe, it 

 inflames so easily, and often produces such violent explosions : 

 while sodium can be employed without fear, since it may be 

 raised in the atmosphere to a higher temperature than its point 

 of fusion — indeed, we have reason to believe that it is in- 

 flammable only in a state of vapour, though still at a tempera- 

 ture below its boiling point ; and, if it is kept very carefully 

 from water, there will be little likelihood of its taking fire. 



To get pure aluminium by Deville's method, we require 

 pure alumina, pure chloride of aluminium, and metallic sodium : 

 for any impurities present in these will be concentrated in the 

 aluminium, and affect its properties very much : nor, if once 

 combined with it, can they ever be entirely removed. We shall 

 first, therefore, describe how these are to be had. 



To obtain 'pure alumina. — Eight and a half parts, by weight, 

 of the sulphate of alumina of commerce, for every required 



