PROCEEDINGS 



OF THE 



AMERICAN ACADEMY 



OF 



ARTS AND SCIENCES. 



VOL. XXVIII. 



PAPERS READ BEFORE THE ACADEMY. 



L 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY 

 OF HARVARD COLLEGE. 



A REVISION OF THE ATOMIC WEIGHT OF BARIUM. 

 FIRST PAPER : THE ANALYSIS OF BARIC BROMIDE. 



By Theodore William Eichards. 



Presented January 11, 1893. 

 Table of Contents. 



Introduction 



Balance and Weights 



Spectroscopic Detection of Calcium, 



Strontium, and Barium . . . . 



Choice of Material 



PAGE 



1 



PAGE 



Properties of Baric Bromide .... 11 



Preparation of Materials 16 



Method of Analysis 23 



Data and Results 26 



The Atomic Weight of Barium . . 30 



Introduction. 



Ill the course of a recent determination of the atomic weight of 

 copper,* there was an attempt made to determine the ratio of cupric 

 to baric sulphate; but in the discussion of the result it became 

 evident that the ordinary method of precipitation was far too crude 

 for the desired purpose. Moreover, even had there not been pos- 

 sible errors of a serious nature in the method, the atomic weight of 

 barium was evidently too uncertain to form the basis of any accu- 

 rate comparison. Hence this attempt was at the time given up, 



* These Proceedings, Vol. XXVI. p. 258. 



VOL. XXVIII. (n. 8. XX.) 1 



