﻿Ions and the Relative lonization-Powei> of Solvents. 393 



calculate the velocity of tbe hydrogen ion; and from the same 

 constants for a solution of (say) sodium or potassium acetate, 

 we can get the velocity of the acetic-acid group C 2 H 3 2 . If 

 we calculate what conductivity these velocities would give to 

 a solution of acetic acid (whose ions nre H and C 2 H 3 2 ) 

 of strength 0*1 gram equivalent per litre, we obtain a number 

 greater than the observed result in the ratio of 3168 to 40. 



In order to observe whether the velocity of the ions was 

 reduced in the same proportion as the conductivity, the 

 velocity of the hydrogen ion through a solution of sodium 

 acetate was determined by Lodge's method. 



The apparatus used is represented in 

 the figure, and was the same as that 

 employed in the earlier investigation 

 above mentioned. Ordinary aqueous 

 solutions were at first set up ; but the 

 junction did not travel uniformly, and 

 agar jelly solutions were found to be 

 much better for this purpose. A pre- 

 liminary investigation was made to 

 examine the influence of the jelly. 



The velocity of the bichromic-acid 

 group when driven by a potential gra- 

 dient of one volt per centimetre was 

 determined by filling the longer limb of 

 the tube with a solution of potassium 

 bichromate in agar jelly just strong 

 enough to set, and the shorter with a 

 similar solution of potassium chloride. 

 A current was then passed across the 

 junction by connecting the electrodes 

 with a battery of storage -cells giving 

 an electromotive force of about 50 volts. 

 The bichromic-acid group travels in a 

 direction opposite to that of the current 

 and displaces the chlorine, so that the 

 colour-boundary moves. If v represents the observed velo- 

 city, A the area of cross section of the tube at the point of 

 junction of the solutions, r the specific resistance of the solu- 

 tion, and 7 the strength of current as shown by a galvano- 

 meter empirically graduated by means of a DanielFs cell ami 

 box of resistance-coils, it is easy to prove that the specific 

 ionic velocity of the ion causing the change of colour is 



k 



-4t?^ 



• 



vA 



