510 ALUMINUM. 



ORDER III. 



METALLIC BASES OF THE EARTHS. 

 SECTION VIII. 



ALUMINUM. 

 Eg. 171.2, or 13.72; Al. 



This element is named from alumen, the Latin term for 

 alum, which is a double salt, consisting of sulphate of alumina 

 and sulphate of potash. 



Like the preceding metal, aluminum is obtained from its 

 chloride, by the action of potassium. But the decomposition 

 must be effected in a platinum or porcelain crucible, as the 

 heat evolved from the reaction, which occurs, would fuse glass. 

 Eight or 10 grains of potassium are covered by a quantity of 

 anhydrous chloride of aluminum, containing, as nearly as pos- 

 sible, the proportion of chlorine equivalent to the potassium ; 

 the lid of the crucible is fastened down by a wire, and the heat 

 of a lamp applied. The action which follows is violent, and 

 attended with the evolution of much heat. The aluminum is 

 afterwards separated from the chloride of potassium, with which 

 it is mixt, by digesting the crucible and its contents in a con- 

 siderable quantity of cold water. The metal appears as a grey 

 powder, resembling spongy platinum, but is seen in a strong 

 light, while suspended in water, to consist of small scales or 

 spangles having the metallic lustre. It is not a conductor of 

 electricity when in this divided state, but becomes one when 

 its particles are approximated by fusion. Wohler finds that 

 iron resembles aluminum in that respect. 



Aluminum has no action upon water at the usual tempera- 

 ture, but decomposes it to a small extent, at the boiling tem- 

 perature, with the evolution of hydrogen. It undergoes oxi- 

 dation more rapidly in solutions of potash, soda and ammonia, 

 and the resulting alumina is dissolved by these alkalies. Alu- 

 minum requires for fusion a temperature higher than that at 

 which cast iron melts. Heated in open air it takes fire and 

 burns with a vivid light, and in oxygen gas with the production 

 of so much heat as to fuse the alumina, which then has a yel- 



