LITHIUM. 87 



LITHIUM. 



The earlier determinations of the atomic weight of hthium 

 b}^ Arfvedson, Stromeyer, C. G. Gmehn, and Kralovanzky 

 were all erroneous, because of the presence of sodium com- 

 pounds in the material employed. The results of Berzelius, 

 Hagen, and Hermann were also incorrect, and need no 

 further notice here. The only investigations which we need 

 to consider are those of Mallet, Diehl, Troost, and Stas. * 



Mallet's experiments* were conducted upon lithium chlo- 

 ride, which had been purified as completely as possible. In 

 two trials the chloride was precipitated by nitrate of silver, 

 which was collected upon a filter and estimated in the ordi- 

 nary way. The figures in the third column represent the 

 LiCl proportional to 100 parts of AgCl : 



7.1885 gmi. LiCl gave 24.3086 grm. AgCl. 29.606 



8.5947 " 29.0621 " 29.574 



In a third experiment the LiCl was titrated with a standard 

 solution of silver. 3.9942 grm. LiCl balanced 10.1702 grm. 

 Ag, equivalent to 13.511 grm. AgCl. Hence 100 AgCl = 

 29.5(33 LiCl. Mean of all three experiments, 29.581, ± .0087. 

 Diehl,t whose paper begins with a good resume of all the 

 earlier determinations, describes experiments made with 

 lithium carbonate. This salt, which was spectroscopically 

 pure, was dried at 130° before weighing. It was then 

 placed in an apparatus from which the carbon dioxide gen- 

 erated by the action of pure sulphuric acid upon it could 

 be expelled, and the loss of weight determined. From this 

 loss the following percentages of COj in Li^COg were deter- 

 mined : 



59.422 



59.404 



59.440 



59.401 



Mean, 59.417, ± .006 



* Silliman's Amer. Journal, November, 1856. Chem. Gazeti-e, 15, 7. 

 f Ann. Chem. Pharm., 121, 93. 



