152 THE ATOMIC WEIGHTS. 



calcining the oxalate, and retained an admixture of car- 

 bon. Many such points were worked up by Rammelsberg 

 with much care, so that his papers should be scrupulously 

 studied by any chemist who contemplates a redetermination 

 of the atomic weight of uranium. 



In 1841 and 1842 Peligot published certain papers* show- 

 ing that the atomic weight of uranium must be somewhere 

 near 120. A few years later the same chemist published 

 fuller data concerning the constant in ciuestion, but in the 

 time intervening between his earlier and his iinal researches 

 other determinations were made by Ebelmen and by Wer- 

 theim. These investigations we may properly discuss in 

 chronological order. For present purposes the early work 

 of Peligot may be dismissed as only preliminary in charac- 

 ter. It showed that what had been previously regarded as 

 metallic uranium was in reality an oxide, but gave figures 

 for the atomic weight of the metal which were merely 

 approximations. 



Ebelmen'sf determinations of the atomic weight of urani- 

 um were based upon analyses of uranic oxalate. This salt 

 was dried at 100°, and then, in weighed amount, ignited in 

 hydrogen. The residual uranous oxide was weighed, and 

 in some cases converted into U3O4 by heating in oxygen. 

 The following weights are reduced to a vacuum standard : 



10.1644 y"^- oxalate gave 7.2939 grm. UO. 



Reducing these figures to percentages, we may present 

 the results in two columns. Column A gives the percentages 

 of UO in the oxalate, while B represents the amount of 

 U3O4 formed from 100 parts of UO: 



* Compt. Rend., 12, 735. 1841. Ann. Chim. Phys., (3,) 55. 1842. 

 f Journ. fiir Prakt. Chem., 27, 385. 1842. 



