ALUMINUM. 157 



sublimed over iron filings, and finally resublimed from 

 metallic aluminum. Each sample used was collected in a 

 small glass tube, after sublimation from aluminum in a 

 a stream of dry hydrogen, and hermetically enclosed. Hav- 

 ing been weighed in the tube, it was dissolved in water, and 

 the quantity of silver necessary for precipitating the chlo- 

 rine was determined. Reducing to a common standard, his 

 weighings give the quantities of Al2Clg stated in the third 

 column, as proportional to 100 parts of silver : 



1.8786 grin. Al,Cle = 4.543 grm. Ag. 41-352 



3.021 " 7.292 " 41.459— Bad. 



2.399 " 5.S02 " 41-348 



1.922 " 4-6525 " 4I-3II 



1.697 " 4-IOI5 " 41-375 



4.3165 " 10.44S " 41-314 



6.728 " 16.265 " 41-365 



In the second experiment the AUClg contained traces of 

 iron. Rejecting this experiment the remaining six give a 

 mean of 41.344, ± .007. flence Al = 27.441, ± .082. 



In consequence of these figures of Dumas, the atomic 

 weight of aluminum has generally of late years been put at 

 27.5, and the lower results deduced from the work of other 

 investigators have been disregarded. 



In 1879 Terrell* published a new determination of the 

 atomic weight under consideration, based upon a direct 

 comparison of the metal with hydrogen. Metallic alumi- 

 num, contained in a tube of hard glass, was heated strongly 

 in a current of dry hydrochloric acid. Hydrogen was set 

 free, and was collected over a strong solution of caustic 

 potash. 0.410 grm. of aluminum thus were found equiva- 

 lent to 508.2 cc, or .0455 grm. of hydrogen. Hence Al = 

 27.033. 



About a year after Terrell's determination appeared the 

 lower value for aluminum was thoroughly confirmed by J. 

 W. Mallet.f After giving a full resume of the work done 

 by others, exclusive of Isnard, the author describes his own 

 experiments, which may be summarized as follows : 



* Bulletin de la Soc. Chimique, 31, 153. 

 f Phil. Tran*;., 18S0, p. 1003. 



