198 THE ATOMIC WEIGHTS. 



Kessler 53-623, ==.015 



Cooke 53.066, ±.0096 



General mean 53.2311, ±: .cx)8 



The results thus obtained with SbCL confirmed Dumas' 

 determination of the atomic weight of antimony as remark- 

 ably as the syntheses of Sb^Sg had sustained the work of 

 Schneider. Evident]}^, in one or the other series a constant 

 error must be hidden, and much time was spent by Cooke 

 in searching for it. It was eventually found that the chlo- 

 ride of antimony invariably contained traces of oxychloride, 

 an impurity which tended to increase the apparent atomic 

 weight of the metal under consideration. If was also found, 

 in the course of the investigation, that hydrochloric acid 

 solutions of antimonious compounds oxidize in the air dur- 

 ing boiling as rapidly as ferrous compounds ; a fact which 

 explains the high values for antimony found by Kessler. 



In order to render " assurance doubly sure," Professor 

 Cooke also undertook the analysis of the bromide and the 

 iodide of antimony. The bromide, SbBrj, was prepared by 

 adding the finely powdered metal to a solution of bromine 

 in carbon disulphide. It was purified by repeated distilla- 

 tion over pulverized antimony, and by several recrystalliza- 

 tions from bisulphide of carbon. The bromine determina- 

 tions resembled those of chlorine, and gave, if Ag = 108 

 and Br = 80, a mean value for antimony of Sb = 120. 

 Reduced to a common standard, the fifteen analyses give 

 the subjoined quantities of SbBrj proportional to 100 parts 

 of silver bromide : 



1. 8621 grm. SbBij gave 2.9216 grm. AgBr. 63.736 



.9856 " 1-5422 " 63.909 



1.8650 " 2.9268 " 63.721 



1.5330 " 2.4030 " 63.795 



1.3689 " 2.1445 " 63.833 



I. 2124 " I. 8991 " 63.841 



.9417 " 1.4749 " 63.848 



2.5404 " 3.9755 " 63.901 



1.5269 " 2.3905 " 63.874 



1.8604 " 2.9180 " 63.756 



1.7298 " 2.70S3 " 63.870 



