ATOMIC WEIGHTS 191 



A careful study of Eichards' paper will show that, although the last 

 two experiments are probably the best, they are not entitled to such 

 preponderance of weight as the " probable error " here computed would 

 give them. If all of the determinations are assigned equal weight, and 

 treated as one series, the mean becomes 96.520, ±.0025, but this figure 

 is not satisfactory. The four series are unequal in merit, and that 

 fact may be fairly recognized by combining the first and second series 

 into one, and the third and fourth series similarly. On this basis the 

 combination of all the data assumes the following form : 



Pelouze 96.457, it .0036 



Marig-nac 96.360, ± .0024 



Dumas 96.316, ± .0055 



Richards, Series 1, 2 96.5165, ± .0040 



Richards, Series 3, 4 96.5255, ± .0010 



General mean 96.4947, ± .00086 



Eichards' determinations alone give Ba= 137.345. 

 The ratio between silver and crystallized barium chloride has been 

 fixed by Marignac.^ The usual method was employed, and two series 

 of experiments were made, in the second of which the water of crystal- 

 lization was also determined. Five grammes of chloride were taken in 

 each determination, to which the subjoined weights of silver correspond. 

 The ratio to 100 parts of silver is given in the second column : 

 Weight Ag. Ratio. 



r 4.4205 113.109 



B J 4.4195 113.135 



[ 4.4210 113.097 



r4.4195 113.135 



A i 4.4200 113.122 



[4.4215 113.060 



Mean, 113.110, ± .0079 



Hence Ba = 137.098. 



The direct ratio between the chlorides of silver and barium has been 

 measured by Berzelius, Turner, Eichards and Thorpe. Berzelius ^ found 

 of barium chloride j)roportional to 100 parts of silver chloride — 



72.432 

 72.422 



Mean, 72.427 

 Hence Ba = 136.714. 



'Arch. Sci. Phys. Nat., 1, 2(i9. 1858. Journ. prakt. Cliem., 74, 212. Oeuvrcs Completes, 1, 550. 

 - Poggend. Annalen, 8, 177. 



