CHLORIDE OF ALUMINIUM. 299 



added, all of the original lime is re-formed and chlorine 

 is evolved. 



751. CHLORIDE OF ALUMINIUM. This 



How is chlo- 



ride of alumi- salt is of peculiar interest and importance, 

 "pared*? *' * n v * ew ^ * ts employment in the prepara- 

 tion of the new metal aluminium. It is 

 prepared by heating alumina at the same time with car- 

 bon and chlorine. The alumina is torn asunder, as it 

 were, by the affinities which are thus brought into play. 

 The carbon takes its oxygen and passes off with it as car- 

 bonic oxide, while the chlorine takes the metal and es- 

 capes with it as volatile chloride of aluminium. The 

 carbon in the process is supplied by coal tar. The 

 process is conducted in iron retorts, the materials hav- 

 ing been previously ignited together before their intro- 

 duction. 



How is it pu- 75%- The chloride is impure, from the 

 rifted? presence of volatile sesquichloride of iron. 



This is separated by leading the uncondensed vapors 

 over highly heated points of iron. The iron has the 

 effect of removing part of the chlorine from the ses- 

 quichloride of iron and reducing it to a non-volatile 

 protochloride. It is thus stopped in its course, while 

 the chloride of aluminium passes on unaffected. It con- 

 denses in the cooler part of the apparatus, in the 

 form of colorless transparent crystals. 



753. COLORED FLAMES. A series of 



What is said . 



of colored beautiful name experiments may be made 



flames? 



assumes different colors according to the chloride em- 

 ployed. Chloride of sodium or common salt, gives 



