OF ARTS AND SCIENCES. 251 



XL 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



THE ATOMIC WEIGHT OF ANTIMONY. 



PRELIMINARY NOTICE OF ADDITIONAL EXPERIMENTS. 



By Josiah P. Cooke. 



Erving Professor of Chemistry and Mineralogy. 

 Presented March 10, 1880. 



In our previous paper on this subject,* we gave our reasons for the 

 opinion, since fully confirmed, that the bromide of antimony is the 

 most suitable compound of this element, as yet known, for determin- 

 ing its atomic weight ; and the results of fifteen analyses of five dif- 

 ferent preparations of the bromide were published, which gave for 

 the atomic weight in question the mean value 120.00 with an extreme 

 variation between 119.4 and 120.4 for all the fifteen analyses, and be- 

 tween 119.6 and 120.3 for the six determinations in which we placed 

 most confidence. The antimouious bromide used in these determina- 

 tions was purified first by fractional distillation, and secondly by crys- 

 tallization from a solution in sulphide of carbon. In the crystallized 

 product thus obtained, the bromine was determined gravimetrically as 

 bromide of silver in the usual way. Although it seemed at the time 

 that the results were as accordant as the analytical process would 

 yield under the unfavorable conditions, which the presence of a large 

 amount of tartaric acid in the solution of the bromide of antimony 

 necessarily involved ; yet it was obvious that the agreement was far 

 from that which was desirable in the determination of an atomic 

 weight, and our chief confidence in the accuracy of the mean value — 



* These Proceedings, Vol. XII. page 1. 



