2 PROCEEDINGS OF THE AMERICAN ACADEMY 



and the plausibility of the single result obtained was ascribed to 

 a chance elimination of opposite errors. 



During the earl}^ part of this century, a number of chemists have 

 investigated the atomic weight of barium with very widel}^ varying 

 results. The first experiments worthy of mention were made by 

 Berzelius and Klaproth;* but these are now of historical interest 

 only. In 1818 the problem was again undertaken by Berzelius, f 

 who found that from 100.00 parts of anhydrous baric chloride he 

 could obtain 138.07 parts of argentic chloride; whence the atomic 

 weight is readily computed to be 136.8. At the same time he 

 found that the same amount of baric chloride yielded 112.175 parts 

 of baric sulphate, which gives Ba = 135.6. 



In 1829 Edward Turnel- J published a redetermination of the 

 latter ratio, finding the equivalents to be as 100.00 : 112.19. He 

 too weighed the argentic chloride obtainable from a given amount 

 of baric chloride, and arrived at the conclusion that the atomic 

 weight of barium could not be far from 137.45. Two years later 

 T. Thomson § described several attempts to weigh barium as the 

 sulphate, which need not be further discussed. In 1833 Turner || 

 found as a mean of three experiments that 112.03 parts of baric 

 nitrate were required to form 100.00 parts of baric suljihate; a re- 

 sult indicating 137.0 as the atomic weight of barium. Ten years 

 later Salvetat ^ published a very incomplete account of the quanti- 

 tative study of the conversion of baric carbonate into sulphate, 

 giving a final result of 136. 



Soon after this both Pelouze ** and Marignac ft determined the 

 ratio of baric chloride to metallic silver, the first finding the atomic 

 weight of barium to be 137.3, and the second 137.1. In 1850 

 Levol tt reduced auric chloride with sulphurous anhydride, and de- 

 termined the sulphuric acid which resulted with baric chloride. 

 Kecalculated with the recently determined atomic weight of gold, 

 197.3, §§ these results give 138.3 as the atomic weight of barium. 



* See Wollaston, Pliil. Trans., 1814, p. 20. 



t Pogg. Annalen, VIII. 189. 



t Phil. Transactions, 1829, p. 296. 



§ System of Chemistry, 7th Edition, 1831, I. 426. 



II Phil. Transactions, 183.3, p. 538. 



1[ Compt. Rend , XVII. 318. ** Ibid., XX. 1047. 



tt Liebig's Annalen, 1848, LXVIII. 215. 

 Jt Ann. Chim. Phys., [3.] XXX. 359. 

 §§ Kruss, 1887 ; Thorpe and Laurie, 1887 ; and Mallet, 1889. 



