Chemistry. 177 



. i 



22. On Aluminium and some of its Compounds. — By Dr Wohler. 

 (PoggendorfF's Anna/en, xi. 146.) — Some years ago, Professor Oersted suc- 

 ceeded in forming a volatile compound of chlorine and aluminium, by trans- 

 mitting dry chlorine gas over a mixture of alumina and charcoal heated to 

 redness. By acting on this chloride with an amalgame of potassium, he 

 procured an amalgame of aluminium, from which, by the aid of heat, the 

 mercury was expelled, and there remained a metallic mass of the colour 

 and lustre of tin, and supposed to be aluminium. On repeating these ex- 

 periments at the request of Professor Oersted, Dr Wohler failed in pro- 

 curing aluminium, the metallic mass which remained after the separation 

 of the mercury proving to be potassium ; but by another process of his own 

 contrivance he was so fortunate as to procure aluminium in a pure state. 



23. Chloride of Aluminium. — To prepare this compound, from which 

 the aluminium is procured, Dr Wohler precipitated the aluminous earth 

 from a hot solution of alum by carbonate of potash in excess, washed the 

 precipitate on a filter, and dried it. From the mode of preparation, the 

 hydrate of alumina contained a little potash in combination, but its pre- 

 sence does not interfere with the success of the process. The hydrate was 

 mixed with charcoal in powder, sugar, and oil, so as to form a thick paste, 

 and was then heated in a covered crucible until all the organic matter was 

 destroyed. By this means the alumina was brought into a state of inti- 

 mate mixture with finely divided charcoal, and in this state was placed, 

 while yet hot, in a tube of porcelain, which was fixed in a convenient fur- 

 nace. After expelling the air within the apparatus by a current of dry 

 chlorine, the tube was brought to a red heat. The formation of the chlo- 

 ride of aluminium then commenced, and continued, with disengagement of 

 carbonic oxide gas, during an hour and a half, when the interior of the 

 porcelain tube became impervious from the sublimed chloride of aluminium 

 collected within it, so that the process was necessarily discontinued. 



On taking down the apparatus a large quantity of the chloride was ob- 

 tained, of a pale greenish-yellow tint, partially translucent, and of a highly 

 crystalline lamellated texture, somewhat like talc ; but no regular crystals 

 could be detected. On exposure to the air it fumed slightly, emitted an 

 odour of muriatic acid gas, and soon deliquesced, yielding a clear liquid. 

 When thrown into water it is speedily dissolved with a hissing noise; and 

 so much heat is evolved that the water, if in small quantity, is brought 

 into a state of brisk v ebullition. The solution is the common muriate of 

 alumina, obviously formed at the expence of the water. According to Oer- 

 sted it is volatile at a point little higher than 212°, and its point of lique- 

 faction is nearly at the same degree. 



Sulphuretted hydrogen has a remarkable action on the chloride of alu- 

 minium, forming with it a compound which contains sulphur, hydrogen, 

 chlorine, and aluminium, though it is not known in what manner these 

 elements are combined. The substance was procured by subliming the 

 chloride of aluminium in a small retort, through which a rapid current of 

 dry sulphuretted hydrogen gas was transmitted ; and the excess of this 

 VOL. ]X. NO. I. JULY 1828. M 



