L50 PROCEEDINGS OP THE AMERICAN ACADEMY. 



becomi igible with a given current density, the deposition of 



hydrogen interferes with the exact determination oi the electrochemical 

 equivalent, even before hydrogen is actually evolved in bubbles, Hence 

 the use of a small cathode is dangerous beyond a limit which depends 

 upon tlif accuracy required. With Bmall current density an approxin 

 correction may be made for the area of the cathode. 



o. Some possible causes of error in the diver voltameter are obviated 

 by a -imple device; and with the help of this apparatus the older 

 methods arc compared with one another. The danger ut' a fallacy in 

 Buch a comparison is pointed out. 



G. The electrochemical equivalent of silver appears to be about 

 0.001 1 172 gram per ampere per second. 



7. The electrochemical equivalent of copper appears to be between 

 O.OOOo-'.Uo and U.<»(iii.;_':il'."j grain per ampere per second. 



8. The discrepancy between the chemical atomic weights of copper 

 and silver and their electrochemical equivalents is explained : hence 

 Faraday's law is verified with two cathions more precisely than before. 

 Conversely, assuming Faraday's law to hold rigidly, and the value f,.'j.C0 

 to represent the true atomic weight of copper, the agreeraeut furnishes 

 evidence of the accuracy of the new method. 



Harvard University, Cambridge, Mass., 

 October 14, 1899. 



