tidO SEPARATION OF ALUMIl 



Procefs for feparating Aluminefrom Alum. In anjvierto the En-^ 

 quiries of R. T. By Mr. Frederick Accum. 



To Mr. NICHOLSON. 

 SIR, 



If you have not received a better anfwer to the queries of your 

 correfpondent R.T. (p. 141) who finds fo much difficulty in ob- 

 taining alumine in a ftate of purity, &c. I requeft you will 

 give a place to the following lines in your next. I have en- 

 deavoured to be as concife aspoffible, and have the honour to be. 

 Sir, 



Your moft obedient humble fervant, 



FREDERICK ACCUM, 

 Old Compton-Street, Soho, 

 July 17, 1804-. 



•ommon procefs The procefs in general recommended by fyftematic writers 

 for feparating f^j obtaining alumine, (which R. T. adhered to) is abfolutely 

 aluminefrom " ,u r i u a a -c r 



alum, throws erroneous, for no pure earth or alum can be expected it a fo- 



down a fait, and jution of alum of commerce be decompofed by a folution of 

 earth. ^ carbonated alcali, and fubfequent ablution and expulfion of the 



carbonic acid. For alum of commerce is a triple compound, 

 confifting of alumine, potafh and fulphuric acid in excefs. If 

 we attempt to (aturate this excefs of acid, by the addition of 

 an alcali, or even by pure alumine, a highly infoluble fait, 

 (fulphale of alumine) is generated, differing from alum prin- 

 cipally in the proportion of its conftituent parts. When we 

 therefore gradually add (as R. T. did) to a folution of alum, a 

 carbonated alcali, the fii ft effedt of it is, to faturate the excefs 

 of the fulphuric acid, and the precipitate confifts principally 

 of the fait, which is infoluble In water. A farther addition 

 efFeds infiantly a decompofition of part of the fait, which, in 

 proportion as it takes place, becomes mixed with the alumine, 

 which is thus covered or defended from the further a6lion of the 

 alcali. This being the cafe, it is obvious that no' fubfequent 

 wadiing can do more than feparate the fulphate of potafb, and 

 therefore the refuluum, inftead of being pure alumine (as 

 R. T. imagines) contains alfo a variable portion of true ful- 

 phate of alumine. 



