ATOMIC WEIGHTS 



119 



impurities as dissolved air, retained water and ammonia, and nitric or 

 nitrous acids. Only two of these were found, and in minute traces, be- 

 tween 0.001 and 0.003 per cent, in all. The final data, with vacuum 

 weights, are as follows: 



Ag. AgNO^. Ratio. 



6.14837 9.68249 157.481 



4.60825 7.25706 157.480 



4.97925 7.84131 157.480 



9.07101 14.28503 157.480 



9.13702 14.38903 157.481 



9.01782 14.20123 157.480 



Mean, 157.480, ± .0001 



The impurities above mentioned may lower this value to 157.478, their 

 maximum effect. The authors accept the intermediate figure, 157.479. 

 Combining the several determinations, we have- — 



Penny 157.4417, ± .0033 



Marignac 157.449, ±: .0061 



Stas, earlier 157.474, ± .0014 



Stas, later 157.486, ± .0003 



Hardin 157.484, ± .0020 



Richards and Forbes 157.479, ± .0001 



General mean 157.479, it .000095 



For the direct ratio between silver nitrate and silver chloride there are 

 two series of estimations. A weighed quantity of nitrate is easily con- 

 verted into chloride, and the weight of the latter ascertained. In two 

 experiments Turner ' found of chloride from 100 parts of nitrate : 



84.357 

 84.389 



Mean, 84.373, ± .011 



Penny,' in five determinations, found the following percentages; 



84.370 

 84.388 

 84.377 

 84.367 

 84.370 



Mean, 84.3744, ± .0025 

 The general mean from both series is 84.3743, ±.0025. 



1 Phil. Trans., 1833. 537. 



2 Phil. Trans., 1839. 



