RICHARDS AND HEIMROD. — THE IMPROVED VOLTAMETER. 441 



and Patterson and Guthe have attracted most attention. Since the first 

 three investigations used a voltameter of the original Lord llayleigh 

 type, a correction of —0.05 per cent should be applied to each. More- 

 over, Kohlrausch and Kahle did not heat their deposits to redness ; 

 hence an additional reduction of about 0.016 per cent* is necessary. 

 Finally, Kohlrausch deposited the silver on a silver kathode, while 

 Lord Rayleigh and Kahle made tlieir determinations with platinum 

 kathodes — a correction which leads to a further reduction of .01 per 

 cent for Kohlrausch's value, or 0.076 in all. Patterson and Guthe, on 

 the other hand, deposited the silver on platinum, but used old solutions 

 saturated with silver oxide. Such solutions may have yielded about 

 0.135 more silver than the standard. When the correction for heating 

 is added to this the total reduction becomes 0.15 per cent. Thus we are 

 led to the following table : — 



TABLE XVL 



The Corrected Electrochemical Equivalent of Silver. 



(1) Lord Rayleigh and Mrs. Sidgwick,t 0.0011179 -0.050% 0.0011173 



(2) Fr. «fe W. Kohlrausch,! 0.001 1183 -0.07G 0.0011175 



(3) Kahle,§ 0.0011183 -0.066 0.0011176 



(4) Patterson & Guthe, II 0.0011192-0.150 0.0011175 



Average 0.0011175 



The greatest deviation from this average is 0.02 per cent, a remark- 

 able agreement considering the variety of physical method used by the 

 experimenters. Lord Rayleigh and Kahle used an electro-dynamometer 

 and Kohlrausch an accurate tangent galvanometer for the calculation of 

 the current, while Patterson and Guthe made themselves entirely free 

 from the acceleration of gravity or the strength of the magnetic field by 

 means of an absolute electro-dynamometer. Hence for the present the 

 great bulk of evidence seems to favor the value 0.0011175, the mean of 

 four entirely independent determinations, as the true electrochemical 

 equivalent of silver. Our data also give the electrochemical equivalent 

 of copper in the cupric condition as 0.00032929 gram per ampere per 

 second. 



The number of coulombs attached to one gram equivalent of any 

 electrolyte is therefore 96,580. 



* The average of Lord Rayleigh's results and ours. 



t Phil. Trans., 175, 411 (1884). J Wied. Ann. N. F., 27, p. 1 (1886). 



§ Wied. Ann. N. F., 67, 1 (1809). 1| Vhys. Review, 7, 257 (1898). 



