156 THE ATU.MIC WEIGHTS. 



ALUMINUM. 



The atomic weight of ahiminum has been determined by 

 Berzelius, Mather, Tissier, Dumas, Isnard, Terreil, and 

 Mallet. The early calculations of Davy and of Thomson 

 we may properly disregard. 



Berzelius' * determination rests upon a single experiment. 

 He ignited 10 grammes of dry aluminum sulphate, 

 Al2(S04)3, and obtained 2.9934 grammes of AUOg as resi- 

 due. Hence, if S = 31.987 and O = 15.9633, Al = 27.243. 



In 1835 1 Mather published a single analysis of aluminum 

 chloride, from which he sought to fix the atomic weight of 

 the metal. 0.646 grm. of Al2Cle gave him 2.056 of AgCl 

 and 0.2975 of AljOg. These figures give worthless values 

 for Al, and are included here only for the sake of complete- 

 ness. From the ratio between AgCl and Al 2 CI g , Al = 28.925. 



Tissier'sJ determination, also resting on a single experi- 

 ment, appeared in 1858. Metallic aluminum, containing 

 .135 per cent, of sodium, was dissolved in hydrochloric acid. 

 The solution was evaporated with nitric acid to expel all 

 chlorine, and the residue was strongly ignited until only 

 alumina remained. 1.935 grm. of Al gave 3.645 grm of 

 AI2O3. If we correct for the trace of sodium in the alumi- 

 num, we have Al = 27.073. 



Essentially the same method of determination was adopted 

 by Isnard, II who, although not next in chronological order, 

 may fittingly be mentioned here. He found that 9 grm. of 

 aluminum gave 27 grm. of AI2O3. Hence Al = 26.938. 



In 1858 Dumas,§ in connection with his celebrated revi- 

 sion of the atomic weights, made seven experiments with 

 aluminum chloride. The material was prepared in quantity, 



* Poggend. Annal., 8, 177. 



■f Silliman's Amer. Journ., 27, 241. 



X Compt. Rend., 46, 1105. 



II Compt. Rend., 66, 508. 1868. 



^ Ann. Chim. Phys., (3,) 55, 151. Ann. Chem. Pliann., 113, 26. 



