JOURNAL 



OF THE . 



WASHINGTON ACADEMY OF SCIENCES 



Vol. IV DECEMBER 19, 1914 No. 21 



PHYSICS. — Studies on the silver voltameter.^ G. A. Hulett 

 and G. W. Vinal, Bureau of Standards. 



A comparison has been made of the silver voltameters and 

 methods employed at the Bureau of Standards with the volta- 

 meters and methods used at Princeton University. For the 

 details of the previous work at these two institutions reference 

 is made to the Bureau of Standards Bulletin, 9, 151, 209, 493; 

 10, 475, and the Transactions of American Electrochemical 

 Society, 12, 257; 22, 367. All the experimental data recorded 

 in this paper were obtained in the laboratory of Physical Chem- 

 istry of Princeton University. 



A preliminary comparison of the voltameters, using the same 

 electrolyte in all, showed a consistent difference of one part in 

 ten thousand, the Bureau voltameters having the greater de- 

 posit. A systematic search for the cause of this difference showed 

 it to be due to two factors, viz., the differences in the methods 

 of preparing the porous cups and, second, the differences in the 

 method of washing the deposit. 



The Bureau's porous cups were kept in silver nitrate between 

 experiments and produced little change of acidity in the electro- 

 lyte of the voltameter, but the Princeton porous cups were 

 usually washed free from the silver nitrate after each experiment 

 and kept in distilled water. It was found in this case that the 

 acidity of the voltameter electrolyte increased. The fact that 

 the Bureau's porous cups were made by a different maker than 

 for the Princeton cups was without significance since when the 



I Detailed pcaper to appear in full in the Bulletin of the Bureau of Standards. 



593 



