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XLIX. On the Preparation of Aluminium from Kryolite. 

 By Allan Dick^ Esq.* 



IN the last Number of this Journal there was a translation of 

 a paper of H. Rose of Berlin, describing a method of pre- 

 paring aluminium from kryolite. Previously, at the suggestion 

 of Dr. Percy, 1 had made some experiments on the same subject 

 in the metallurgical laboratory of the School of j\Iines ; and as 

 the results obtained agree closely with those of Rose, it may be 

 interesting to give a short account of theni now, though no de- 

 tailed description was jjublished at the time, a small piece of 

 metal ])repared from kryolite having simply been shown at the 

 weekly meeting of the Royal Institution (March 30, 1855), ac- 

 companied with a few words of explanation by Taraday. 



Shortly after the publication of M. Deville's jn-ocess for pre- 

 paring the metal from chloride of aluminium, along with ]\Ir. 

 Smith I tried to make a specimen of the metal ; but we found it 

 a much more difficult thing to do than Deville's paper had led us 

 to anticipate, and had to remain contented with a much smaller 

 piece than we had hoped to obtain. It is, however, undoubtedly 

 only a matter of time, skill and expense, to join successful prac- 

 tice to the details of M. Deville. 



Whilst making these experiments. Dr. Percy had often re- 

 quested us to try whether kryolite could not be used instead of 

 the chlorides, but some time elapsed before we obtained a spe- 

 cimen of the mineral. 



The first exj)erimeuts were made in glass tubes sealed at one 

 end, into which alternate layers of finely-pounded kryolite and 

 sodium cut into small pieces wei-e introduced, and covered in 

 some instances by a layer of kryolite, in others by one of chloride 

 of sodium. The tube \\as then heated over an air-gas blowpipe 

 for a few minutes, till decomposition had taken place and the 

 ])roduct was melted. When cold, on breaking the tube it was 

 found that the mass was full of small globules of aluminium; 

 but owing to the specific gravity of the metal and flux being 

 nearly alike, the globules had not collected into one I)utton at 

 the bottom : to effect this, long-continued heat would be required, 

 which cannot be given in glass tubes, owing to the powerful 

 action of the melted fluoride upon them. To obviate this difli- 

 culty, a platinum crucible was lined with magnesia, hy I'amming 

 the same hard in, and subsequently cutting out all but a lining. 

 Into this, alternate layers of kryolite and sodium were placed, 

 with a thicklsh layer of kryolite on the top. The crucible was 

 covered with a tight-fitting lid, and heated to redness for about 

 half an hour over the air-blowpipe. When cold, it was placed in 



* Couimuiiicatod by the Author. 



