262 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



ALUMINUM. 



The atomic weight of aluminum has been determined by Berzelius, 

 Mather, Tissier, Dumas, Isnard, Terreil, Mallet, Baubigny, Thomsen and 

 Kohn-Abrest. 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, Al, (804)3, and obtained 2.993-i 

 grammes of AI0O3 as residue. 



Hence Al = 27.31. 



In 1835 Mather ' published a single analysis of aluminum chloride, 

 from which he sought to fix the atomic weight of the metal. 0.646 grm. 

 of AlCL gave him 2.056 of AgCl and 0.2975 of AUOg. These figures give 

 worthless values for Al, and are included here only for the sake of com- 

 pleteness. From the ratio between AgCl and AICI3, Al = 28.737. 



Tissier's ' determination, also resting on a single experiment, appeared 

 in 1858. Metallic aluminum, containing .135 per cent, of sodium, was 

 dissolved in hydrochloric acid. The solution was evaporated with niti'ic 

 acid to expel all chlorine, and the residue w^as 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 aluminum, we have Al = 27.185. 



Essentially the same method of determination was adopted by Isnard,* 

 who, although not next in chronological order, may fittingly be men- 

 tioned here. He found that 9 grm. of aluminum gave 17 grm. of AI0O3. 

 Hence Al=:27. 



In 1858 Dumas," in his celebrated revision of the atomic weights, made 

 seven experiments with aluminum chloride. The material was prepared 

 in quantity, sublimed over iron filings, and finally resublimed from metal- 

 lic aluminum. Each sample used was collected in a small glass. tube, 

 after sublimation from aluminum in a stream of dry hydrogen, and 

 hermetically enclosed. Having been weighed in the tube, it was dissolved 

 in water, and the quantity of silver necessary for precipitating the chlor- 

 ine was determined. Eeducing to a common standard, his weighings 

 give the quantities of AlCL stated in the third column, as proportional 

 to 100 parts of silver: 



' Poggend. Annal., 8, 177. 



^ Amer. Journ. Sci., 27, 241. 



2 Conipt. Rond., 46, 1105. 



* Compt. Rend. , 66, 508. 1868. 



!> Ann. Cliini. Phys. (3), 55, 151. Ann. Chem. Pharm., 113, 26. 



