CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 



HARVARD COLLEGE. 



NOTE CONCERNING THE SILVER COULOMETER. 



By Theodore William Richards. 

 Received August 7, 1908. 



In a recent paper Messrs. Smith, Mather and Lowry have recounted 

 their numerous and carefully executed experiments on the silver volta- 

 meter, or coulometer.! Their results are valuable, for they appear to 

 have shown that it is possible to obtain an accurate result with the 

 silver coulometer without the trouble of interposing either porous cup 

 or siphon between the anode and the cathode. 



One of the respects in which their experiments have differed from 

 those of others is their use of a large volume of electrolyte. It is not 

 surprising that this device tends toward accomplishing the desired end ; 

 for when the volume of the electrolyte is sufficiently large, the anoma- 

 lous substances formed at the anode are so much diluted as to have 

 but slight effect on the cathode. Moreover, the chance that these sub- 

 stances will be affected by dissolved air is much greater in the larger 

 volume. 



Although in this respect the new English work is of great service, 

 there are one or two points in which exception may be taken to the 

 authors' conclusions, and this note is written to call attention to these 

 points. The coming International Meeting upon Electrical Standards 

 renders it desirable that the matter receive promptly as much discus- 

 sion as possible. 



First among the minor points is the much disputed question as to 

 whether silver crystals deposited in the coulometer contain liquid in- 

 clusions. Upon page 570 of their paper Smith and Mather speak of 

 having attempted to test this point by reheating deposits previously 

 dried at 160° to 240° in eight cases and to over 400° on three other 



1 Phil. Trans. Roy. Soc. London., Series A., 207, 545 (1908). 



