BARIUM. 



119 



Dumas* employed barium chloride prepared from pure barium 

 nitrate, and took the extra precaution of fusing the salt at a red heat in 

 a current of dry hydrochloric acid gas. Three series of experiments 

 upon three samples of chloride gave the following results : 



L7585 

 3.8420 

 2.1585 

 4.0162 

 1.6625 

 2.4987 

 3.4468 

 4.0822 

 4.2062 

 4.4564 

 8.6975 

 2.2957 

 4.I372 

 4.2662 



4.4764 

 5.6397 



Ratio. 



9 6 -303 1 



9 6 .339 [ 



96.340 | 

 96.358 j 

 96.265^ 



96-304 



96.306 



96.290 



96.289 



96.271 



96.307 



96.3 l6> | 



96.371 



96.303 \ 



96.3 2 9 

 96-372J 



Mean, 96.333 



>. Mean, 96.290 



Mean, 96.338 



Mean, 96.316, dr .0055 



The work done by Richards f was of a much more elaborate kind, for 

 it involved some collateral investigations as to the effect of heat upon 

 barium chloride, etc. Every precaution was taken to secure the spectro- 

 scopic purity of the material, which was prepared from several sources, 

 and similar care was taken with regard to the silver. For details upon 

 these points the original paper must be consulted. As for the titrations, 

 three methods were adopted, and a special study was made with refer- 

 ence to the accurate determination of the end point ; in which particular 

 the investigations of Pelouze, Marignac, and Dumas were at fault. In the 

 first series of determinations, silver was added in excess, and the latter 

 was measured with a standard solution of hydrochloric acid. The end 

 point was ascertained by titrating backward and forward with silver 

 solution and acid, and was taken as the mean between the two apparent 

 end points thus observed. The results of this series, with weights reduced 

 to vacuum standards, were as follows : 



