EARTHS. 293 



ALUMINIUM.* 



1. HISTORY. 



(a.) Discovered by Sir H. Davy, who obtained, by galvanic pow- 

 er, a compound of iron and this metallic base, which effervesced in 

 water, and produced alumina, and oxide of iron ; also, by passing 

 potassium, in vapor, through alumina heated to whiteness, the potassi- 

 um was converted into potash, and metallic particles were obtained, 

 which became white in the air, and effervesced in water ; when the 

 temperature was only at a red heat, an alloy of the two metals ap- 

 peared to be obtained, which effervesced violently in water, and took 

 fire spontaneously in the air. 



2. NEW PROCESS. 



(a.) Of late, Dr. JVohler has obtained aluminium pure. ^ (The 

 student may omit this process until he has studied chlorine.) Chlo- 

 ride of aluminium is formed by passing dry chlorine gas through an 

 ignited porcelain tube, containing very dry alumina, intimately blend- 

 ed with charcoal, in consequence of its having been mixed in the 

 state of hydrate, and then ignited in a covered crucible, with char- 

 coal, sugar, and oil 5 the hydrate is made by adding an excess of 

 carbonate of potash, to a hot solution of alum. 



(b.) Carbonic oxide gas ivas evolved, and after the chlorine gas 

 had passed for an hour and a half, the sublimed chloride of alumini- 

 um had collected in such quantity as to choke the tube. 



(c.) The chloride was in greenish yellow translucent scales, resem- 

 bling talc, deliquescing into a clear liquid, and combining with water r 

 with heat, and even ebullition, if the quantity of water was small, 

 and muriate of alumina was formed. 



(d.) Potassium decomposes the chloride of aluminium, and evolves 

 the metal. The action is too violent for glass, which is [destroyed 

 by the heat disengaged. It succeeds in a platinum crucible, the 

 cover being secured by wire, and the heat of a spirit lamp applied } 

 but the crucible becomes red hot.} 



(e.) The potassium should be free from carbon, and the quantity 

 not over the size of ten peas> and so proportioned, that none of the 

 chloride may sublime, during the decomposition, nor the resulting 

 mass be alkaline. 



* Aluminum would seem preferable, but I adopt the orthography already intro- 

 duced. 



i The first hint was given by Prof. Oersted, in consequence of his having obtain- 

 ed what he believed to be aluminium, by acting upon chloride of alumina, by an 

 amalgam of potassium. 



t To prevent the possibility of deception, the experiment was repeated in a porce- 

 lain crucible, and with complete success. 



