CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



THE ELECTROCHEMICAL EQUIVALENTS OF 

 COPPER AND SILVER. 



By Theodore William Richards, Edward Collins, and George W. 



Heimrod. 



Presented June 14, 1899. Received October 30, 1899. 



Four years ago we began an investigation which had as its object the 

 careful study of the well known irregularities of the "copper voltameter" 

 from the point of view of the modern theories of electrochemistry. One 

 reason for this study was the fact that the atomic weight of copper com- 

 puted from the relation of its electrochemical equivalent to that of silver 

 was noticeably smaller than the atomic weight obtained in this Labora- 

 tory by purely chemical methods.* Owing to circumstances beyond our 

 control the completion of the work was postponed far beyond its proper 

 time ; but at last it is in a condition suitable for partial publication. The 

 matter was complicated by the discovery of an error in the " silver volta- 

 meter," as well as in the " copper voltameter." In the mean time an 

 extremely interesting paper by Foerster and Seidel, and several other 

 valuable contributions by Kahle, Patterson and Guthe, and others, upon 

 allied subjects, have appeared.j These cover a part of the ground occu- 

 pied by our work, and thereby shorten the present account. The work 

 naturally falls under two headings, because each metal needed its special 

 investigation ; and this natural division will be retained in the following 

 description. 



I. The Copper Voltameter. 



The work of Gore, Lord Rayleigh and Mrs. Sidgwick, Gray, Shaw, 

 Vanni, and Gannon, | showed long ago that a side reaction, varying in 



* T. W. Richards, These Proceedings, 26, 240 (1891). 



t Foerster and Seidel, Zeitschr. anorg. Chem., 14, 106-140 ; K. Knlile, Wied. 

 Ann., 67, 1 (1899) ; Patterson and Guthe, Physical Review, 7, 257 (1808); E. H. 

 Griffiths, Nature, 56, 258 (1897), etc. 



t Gore, Nature, 25, 473 (1882) ; Lord Rayleigh and Mrs. Sidgwick, Pliil. Trans., 

 175, 458 (1884) ; Gray, Piiil. Mag., (5), 22, -389 (1886). also 25, 179(1888) ; Shaw, 

 Brit. Ass. Rep. 1886, p. .318 [Phil. Mag., (5), 23, 138]; Vanni, Wied. Ann., 44, 

 214 (1891) ; Gannon, Proc. Roy. Soc, 55, 66 (1894). 



