232 



REPORT — 1897. 



Note. — The migration data for solutions of copper chloride are not known. 

 The specific ionic velocity of copper at infinite dilution (when it would be inde- 

 pendent of the nature of the combination) is given by Kohlrausch as 0-00031, but in 

 a solution of the strength used it would be considerably less. The sum of the 

 ionic velocities of cobalt chloride in alcohol, as calculated from the conductivity, 

 is 0-000060 cm. per sec, and that of cobalt nitrate 0-000079. These numbers are to 

 be compared with the sum of the observed velocities given in the table — namely, 

 0-000048 and 0000079 respectively. 



The agreement will be seen to be quite as good as can be expected'. 

 The number for the hydrogen ion in acetic acid is especially interesting', 

 for it shows that, in cases where the conductivity is abnormally low, such 

 as those of acetic acid and ammonia, the ionic velocities are reduced in the 

 same proportion. In such cases the mean free time of the ions (adopting 

 the language of the dissociation theory) is small as compared with their 

 mean paired time. They can move forward only while they are free, and 

 thus their velocity is reduced, and, with it, the conductivity of the solution. 

 Kohlrausch's theory, therefore, probably holds good in every case, even if 

 alcohol be the solvent, if the proper values are given to the ionic velocities — 

 i.e. the values which express the velocities with which the ions actually 

 move in the solution of the strength taken, and under the conditions of 

 the experiment. 



If we restrict ourselves to the specific ionic velocities — the velocities 

 at infinite dilution — -we must introduce a factor measuring the ratio of the 

 actual to the limiting relative velocity of the ions. If we call this ratio a, 

 and take u and v to denote the specific ionic velocities, we can express the 

 conductivity by the equation 



a (u + v) 



1-0352 X 10'- 

 n 



or 



k / , X 10-' 



