ATOMIC WEIGHTS 



383 



silver, which, however, sometimes retained minute traces of selenium. 

 The data obtained were as follows : 



Mean, 62.957, ± .0048 

 Hence Se = 78.95. 



Secondly, a warm aqueous solution of selenious acid was mixed with 

 HCl and reduced by a current of SOo. The reduced Se was collected 

 upon a glass filter, dried and weighed. 



General mean, 71.1907, ± .0016 



Ekman and Pettersson's series alone give Se = 79.076. 



Lenher/ in order to determine the atomic weight of selenium, studied 

 two of its compounds. First, silver selenite was heated in a stream of 

 gaseous hydrochloric acid, and so transformed into silver chloride. In 

 a second series of experiments the silver chloride was afterwards reduced 

 to metal by heating in hydrogen. Two ratios were thus determined. 

 For convenience I now treat the two series as one. Lenher's data, with 

 vacuum weights, and with the corresponding percentages added by my- 

 self, are as follows : 



Ag.SeO^ 



AgCl. 



20, 355. 1S9S. Thesis, University of Pennsylvania. 



