66 THE ATOMIC WEIGHTS. 



In the same paper Marignac gives two sets of determina- 

 tions of the percentage of water in crystallized strontium 

 chloride. The first set, corresponding to " B " above, comes 

 out thus : 



40.556 

 40.568 

 40.566 



Mean, 40.563, d= .0024 



In the second set ten grammes of salt were taken at a 



time, and the following percentages were found : 



40.58 



40.59 

 40.58 



Mean, 40.583, ifc .0020 

 General mean, from both series, 40.575, ± .0015 



The chloride used in the series of estimations last given 

 was subsequently employed for ascertaining the ratio be- 

 tween it and the sulphate. Converted directly into sulphate, 

 100 parts of chloride yield the quantities given in the third 

 column : 



5.942 grm. SrClj gave 6. 887 giTn. SrSO^. 115.932 



5-941 " 6.8855 '' 115-949 



5.942 " 6.884 " "5-927 



Mean, 115.936, zfc .004 



Now, to sum up the ratios and calculate the atomic 

 weight of strontium. 



(1.) Ag : SrClj : : 100 : 73.4655, ± .0046 



(2.) Ag : SrCl2.6H,p : : 100 : 123.470, rb .006 



(3.) Per cent, of Ufi in SrCl2.6H20, 40.575, ± .0015 



(4.) SrClj : SrSO^ : : lOO : 1 15.936, =!= .004 



We now have the molecular weight of SrCL,, as follows: 



From (I) SrClj = 158.208, zfc .017 



From (2) " =158.113,^.034 



From (3) " = 157.852, rb .032 



General mean " = 158.124, rb .014 



