74 ATOMIC WEIGHT DETERMINATIONS. 



J. J. Berzelius : 6.533 (0 = 16) ; 40.83 (0 = 100). 



Berzelius found that 1.874 lithium sulphate gave 3.9985 

 barium sulphate, and calculated this relation for S = 200.75 ; 

 Ba = 855.29. He also found 4.4545 melted carbonate = 

 6.653 sulphate, but rejected the analysis. {Lehrbuch, 3, 1229, 

 and Jahresbericht, 10, 1830, 96.) 



R. Hagen : 6.57 (0 = 16). 



Hagen precipitated lithium sulphate with barium chlo- 

 ride, and found that 0.852 dry lithium sulphate gave 1.8195 

 barium sulphate whence he calculates Li := 6.493. [If 

 Ba = 137.08; S = 32 ; this relation gives Li = 6.57.] 

 {Foggend. Ann., 4.8, 1839, 363.) 



J. W. Mallet: 6.95 (0 = 16); 86.89 (O = 100). 



In two experiments a known weight of lithium chloride 

 was precipitated by argentic nitrate, and the argentic chlo- 

 ride weighed. In one experiment lithium chloride was 

 titrated with argentic nitrate by Pelouze's method. The 

 number is the mean; the extreme difference is 0.18 for O 

 = 100. Mallet takes Ag = 1349.66 ; CI = 443.28. The 

 alkalis were separated from the lithium salt by repeated 

 treatment with ether and alcohol. The salt was examined 

 for impurities, and was fused with a little ammonium chlo- 

 ride to prevent the formation of oxy-chloride. {Silliman's 

 Amer. Journ., (2,) 22, 1856, 349.) 



L. Troost: 6.5 (0 = 16). 



Troost found this number from analysis of the carbonate 

 which had been crystallized from water containing carbon 

 di-oxide and dried at 200°, but does not regard it as defini- 

 tive. {Annal. de Chim. et de Phjs., (3,) 51, 1857, 111.) 



J. W. Mallet: 7 (0 = 16). 



Troost having objected to Mallet's former method of 

 determination, he redetermined it by precipitating the 

 sulphate with a standard solution of barium chloride, 

 the precipitating power of which had been tested on the 

 sulphates of magnesium and sodium. This method was 

 adopted to avoid the well-known imperfections of the sul- 

 phur determination. Compared with sodium sulphate the 

 atomic weight of Li was found = 6.92 and 6.95. Compared 

 with magnesium sulphate it was found = 7.07 and 7.09. 



