64 THE QUANTITATIVE SYNTHESIS OF ARGENTIC NITRATE, ETC. 



THE FINAL RESULT AND ITS RELATIONS TO THE VALUES OF ATOMIC 

 WEIGHTS OF NITROGEN AND SILVER. 



The conclusion reached by the foregoing series of experiments is that 

 100.000 parts of silver yield very nearly 157.479 parts of argentic nitrate. 

 Among other experimenters, Penny found 157.442 ; Marignac found 

 157.424; Stas found 157.474 in one series of seven determinations and 

 157.486 in another of two, and Hardin found 157.484. From these older 

 figures, by an interesting coincidence Clarke calculated exactly the value 

 found in the present research. 1 This coincidence is to be attributed not 

 so much to the efficacy of the method of calculation as to the fact that in 

 this case the impurities in the silver happened to balance exactly the im- 

 purities in the argentic nitrate. At first sight it is incomprehensible how 

 Stas, working with slightly impure silver, could have obtained any results 

 higher than the true value ; but it must be remembered that his nitrate was 

 fused in a glass vessel, which must have been attacked by the strongly 

 acid nitrate at 220. Constancy in the weight of the vessel would be no 

 evidence of absence of action, for silver might partly take in the glass the 

 place of the sodium taken from it. Thus a gain in weight due to sodic 

 nitrate might be accompanied with no considerable loss of weight of the 

 vessel. In favor of this hypothesis is the fact that Stas's results steadily 

 decreased in each series, as he proceeded with the work ; the flask seems to 

 have been less and less susceptible to attack, as is reasonable. If the last 

 two determinations of the first series are taken as the most nearly free from 

 this cause of error, the number 157.466 obtained from them should furnish, 

 by comparison with our number, some clue to the amount of gaseous im- 

 purity in Stas's silver. Thus it appears that his silver must have contained 

 nearly 0.01 per cent of impurity probably more if it is considered that 

 the flask was still not wholly resistant a conclusion not very different 

 from that reached by Richards and Wells. 



Speculations of this kind concerning older work are rather a thankless 

 task, however ; there is usually too much that is doubtful to allow them to 

 serve a very valuable purpose. The only object in pursuing the review at 

 all is in order to assure one's self that no real inconsistency exists in the 

 data. 



Recalculation of the Atomic Weights (1897), p. 64. 



