RUBIDIUM. 87 



For lithium itself there are three values : 



From molecular weight LiCl Li = 6.9752, .0051 



From (3^ " 6.9855, .0129 



From (4) " 6.9628, d= .0077 



General mean Li r= 6.9729, .0040 



If 16, Li =- 7.026. From Stas' ratios, Stas found Li = 7.022 ; Ost- 

 wald, 7.0303; Van cler Plaats (A), 7.0273; (B), 7.0235; and Thomsen, 

 7.0307. 



RUBIDIUM. 



i 



The atomic weight of rubidium has been determined by Bunsen, Pic- 

 card, Godeffroy, and Hey cock from analyses of the chloride and bromide. 



Bunsen,* employing ordinary gravimetric methods, estimated the ratio 

 between AgCl and RbCl. His rubidium chloride was purified by frac- 

 tional crystallization of the chloroplatinate. He obtained the following 

 results, to which, in a third column, I add the ratio between RbCl and 

 100 parts of AgCl : 



One grm. RbCl gave 1.1873 grm. AgCl. 84.225 



1.1873 " 84.225 



1.1850 " 84.388 



I. 1880 " 84.175 



Mean, 84.253, db .031 



The work of Piccardf was similar to that of Bunsen. In weighing, 

 the crucible containing the silver chloride was balanced by a precisely 

 similar crucible, in order to avoid the correction for displacement of air. 

 The filter was burned separately from the AgCl, as usual ; but the small 

 amount of material adhering to the ash was reckoned as metallic silver. 

 The rubidium chloride was purified by Bunsen's method. The results, 

 expressed according to the foregoing standard, are as follows : 



I - 1 S&7 S rm - RbCl= 1.372 AgCl -f- .0019 Ag. 84.300 



1.4055 " 1.6632 " .0030 " 84.303 



i. ooi " 1.1850 " .0024 " 84.245 



" 1-7934 " .0018 " 84.313 



Mean, 84.290, d= .0105 

 Godeffroy, J starting with material containing both rubidium and 



*Zeit. Anal. Chem., i, 136. Poggend. Annal., 113, 339. 1861. 



f Journ. fur Prakt. Chem., 86, 454. 1862. Zeit. Anal. Chem., i, 518. 



I Ann. Chem. Pharm., 181, 185. 1876. 



