STRONTIUM. 117 



For the molecular weight of SrCl 2 three estimates are available : 



From (i) SrCI 2 157.390, =}= .0112 



From (2) " = 157.197, .0192 



From (3).... " = 157-123, .'57 



General mean SrCl 2 = 157.281, .0083 



For SrBr 2 there are two values : 



From (5) SrBr 2 = 245.682, .0076 



From (6) " = 245.684, rb .0075 



General mean SrBr 2 = 245.683, .0053 



Finally, with these intermediate data we obtain three independent 

 measures of the atomic weight of strontium, as follows : 



From molecular weight SrCl 2 Sr = 86.923, .0127 



From molecular weight SrBr 2 " = 86.995, =t - OI 35 



From ratio (4) " = 86.434, .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. 



