RICHARDS AND STULL. — FARADAY S LAW. 



413 



FINAL COMPARISON. 



The .largest difference is thus one tenth of a milligram, an amount not 

 much greater than the possible experimental error, while the average 

 difference has sunk to one in twenty thousand. It may be noted that of 

 the six experiments, preliminary and final, four show no significant dif- 

 ference at all. The decreasing average difference with increasing care 

 suggests that the slightly larger weights of silver obtained from the fused 

 salt might be due to reduction of silver by organic dust, which it is dif- 

 ficult wholly to exclude. But even without this explanation, the results 

 are close enough for present purposes, because an accuracy greater than 

 one part in twenty thousand is rarely attained m other physicochemical 

 measurement at the present time. 



Summary. 



In this paper it is shown that a galvanic current deposits essentially 

 the same amount of silver from a solution of argentic nitrate in other 

 nitrates at 250° as it does from an aqueous solution at 20°, within 

 0.005 per cent. Taken in connection with the previous work of 

 Richards, Collins, and Heimrod, this result shows that Faraday's law 

 is not a mere approximation, but is rather to be ranked among the most 

 precise and general of the laws of nature. 



