270 THE ATOMIC WEIGHTS. 



Secondl}^ a warm aqueous solution of selenious acid was mixed with 

 HCl, and reduced by a current of SO,. The reduced Se w^as collected 

 upon a glass filter, dried, and weighed. 



SeO.^. Se. Per cent. Se. 



II. 1760 7.9573 71.199 



II. 2453 8.0053 71-185 



24.4729 17-4232 71.193 



208444 14.8383 71.187 



31.6913 22.5600 71. 191 



Mean, 71.191, rb .0016 

 Sacc found, 71.088, ± .0320 



General mean, 71.1907, ± .0016 



There are now five series of figures from which to deduce the atomic 

 weight of selenium : 



(i.) Per cent, of Se in SeO.^, 71.1907, dz .0016 

 (2.) BaSe03 : BaSO^ : : 100 : 88.437, =b .013 

 (3.) Per cent, of Hg in HgSe, 71.7327, zfc .003 

 (4.) Se : Cl^ : : 100 : 178.696, zb .125 

 (5.) Per cent, of Ag in Ag2Se03, 62.957, dr .005 



From these, computing with — 



O = 15.879, ± .0003 S = 31.828, i .0015 



Ag= 107.108, ± .0031 Ba = 136.392, ± .0086 



CI = 35.179, zh .0048 Hg= 198.491, =b .0083, 



five values for Se are calculable, as follows : 



From (i) Se = 78.477, =b .0049 



From (2) " = 78.006, zb .0410 



From (3) "= 78.217, zt .0095 



From (4) "=78.740,^.0561 



From (5) " = 78.405, zt .0201 



General mean Se ^ 78.419, zh .0042 



If = 16, this becomes Se = 79.016. 



