﻿392 Mr. W. C. D. Whetham on the Velocities of the 



Also, since for our wire p is about *0617 centim., we obtain 

 as approximate values, 



E = 2-00xl0 12 , 



n=7*79xlO n . 

 An experiment with a spring of hard-drawn copper wire gave 



5=2-76, 

 n 



with the approximate values 



E = l*13xl0 12 , 

 w=4-10xlO n . 



XLV. On the Velocities of the Ions and the Relative Ioni- 

 zation-Power of Solvents. By W. C. Dampier Whetham, 

 M.A., Fellow of Trinity College, Cambridge*. 



EROM a knowledge of the electrical conductivity and 

 migration-constant of a solution, Prof. F. Kohlrausch 

 has shown us how to calculate the velocity with which its 

 ions must travel in order that, in accordance with Faraday's 

 law, a given current should be carried (Wied. Ann. xxvi.). 



Prof. 0. Lodge experimentally determined the velocity 

 of the hydrogen ion as it travelled through a jelly solution of 

 sodium chloride and so formed hydrochloric acid, the presence 

 of which was indicated by the decolorization of phenol- 

 phthalein. When the ion was driven by a potential gradient 

 of one volt per centimetre the speed came out 0*0029 centi- 

 metre per second, a number agreeing in a most remarkable 

 manner with Kohlrausch's theoretical value 0*0030 for a 

 decinormal solution (B.A. Report, 1886)* 



The author of this paper has observed the specific ionic 

 velocity of other ions, such as copper and the bichromic-acid 

 group (Cr 2 7 ), by tracing the motion of the junction of two 

 salt-solutions (one of which is of different colour from the other) 

 under the influence of an electric current (Trans. Roy. Soc. 

 1893 A.) . The results agree with Kohlrausch's numbers even 

 in the case of alcoholic solutions, the conductivities of which 

 are much less than those of the corresponding aqueous 

 solutions. 



Certain substances, e. g. ammonia and acetic acid, have 

 been regarded as exceptions to the application of the theory. 

 From a knowledge of the conductivity and migration- 

 constants of acids such as nitric and hydrochloric, we can 

 * Communicated by the Author, 



