STRONTIUM. 117 



For the molecular weight of SrCL three estimates are available : 



From (i) SrClj — 157.390, zfc .0112 



From (2) " =157.197,^.0192 



From (3) " =157.123,^.0157 



General mean SrCl.^ = 157.281, ± .0083 



For SrBr,^ there are two values : 



From (5) SrBPj = 245.682, =b .0076 



From (6) " =245.684,^.0075 



General mean SrBrj = 245.683, ± .0053 



Finally, witli these intermediate data we obtain three independent 

 measures of tlie atomic weight of strontium, as follows : 



From molecular weight SrCl, Sr = 86.923, zb .0127 



From molecular weight SrBr.^ " ^= 86.995, =t .0135 



From ratio (4) . . . " =^ 86.434, it .081 1 



General mean Sr = 86.948, ± .0092 



If = 16, Sr ^= 87.610. Rejection of the third value, which is worth- 

 less, raises these means by 0.01 only. The second value, 86.995, which 

 represents Richards' work, is undoubtedly the best of the three. 



