14 PROCEEDINGS OP THE ACADEMY OF 



about ten per cent, with the slag. This will be explained by the following data. 

 Theoretically: 



• 250 parts of metallic Sodium produce 



100 " " Aluminium; 



VO parts are obtained in one metallic mass ; 

 20 " " in metallic globules ; 



90 " being the nett produce. 

 10 " remain with the scoria. 



Total, 100 



The alkaline scoria contains large quantities of the chloride of sodium, that 

 can be easily extracted by water, leaving an insoluble residue from which the 

 fluoride of aluminium can be extracted by volatilization. The scoria containing 

 the fluoride and the metallic aluminium is economically used by introducing it 

 again with a new charge of the double chloride of aluminium and sodium, and 

 metallic sodium, and by that means the loss of the metal is rendered very small. 



Aluminium, when carefully removed from any slag, is readily fused in a 

 crucible by itself; when in fusion (which is at a lower point than that required 

 to fuse silver) the whole is stirred with a rod, and all the globules of metal are 

 united in one mass with the greatest facility ; at this point nitrate of potash ca,n 

 be added, (the stirring continued.) 



All other metals are oxidized by this process ; the refining is finished when 

 the metal has a pure white color. It can now be poured into a mould of smy 

 shape. 



Impure aluminium may be whitened by plunging it into caustic potash or 

 soda, washing it quickly with distilled water, plunging it again into pure nitric 

 acid, again washing quickly and thoroughly. The surface then has the fine 

 white color of pure aluminium, which it retains unless afterwards polished. 

 This operation has for its object to dissolve out the metals which darken the 

 color of aluminium by their presence. 



Aluminium forms alloys with nearly all the metals, but those which it forms 

 with silver and copper are the most interesting. 



Five parts of aluminium with one hundred parts of pure silver produce 

 an alloy almost as hard as a silver coin, which contains about one-tenth of 

 copper, so that sufficient hardness can be given to silver, without introducing 

 into it a poisonous or an alterable metal. It has the advantage of being worked 

 like silver in a pure state, possessing, however, greater hardness, and being 

 capable of a higher polish. 



Ten parts of aluminium and ninety parts of copper produce an alloy of a pale 

 gold color, possessing great hardness and considerable malleability ; its hard- 

 ness is greater than that of bronze, in the proportion of fifty-one to forty-nine. 

 It can be worked when warm, with the same facility as the best soft iron. 



Twenty parts of aluminium and eighty of copper give to the alloy the color 

 and brilliancy of fine gold, and at the same time sufficient hardness to scratch 

 the alloy of gold employed in coin, without imparing in the slightest degree its 

 malleability. 



By an increase of the per centage of copper in alloys of aluminium the alloy 

 is rendered brittle, showing that the metal must be either used pure or alloyed 

 in small quantities with the copper. 



This explains the peculiar properties ascribed to it by M. Regnault in his in- 

 vestigations on the physical properties of the aluminium prepared by M. Deville, 

 exhibited at the Paris exhibition. 



Numerous experiments have been made (without regard to economy of manu- 

 facture) to obtain the aluminium directly from the oxide alumina, or from the 

 fluoride of aluminium. 



But the results obtained by the use of this double chloride of aluminium and 



[Jan. 



