bo 
the Charges on Ions. Eve | 
of a gas at 15° C. and 760 mm. pressure, then, since a known 
volume of hydrogen is evolved at the negative electrode 
when unit quantity of electricity passes through the liquid, 
the formula 
N x H=1°22 x 10% 
is established, E being measured in electrostatic units. 
If e is the charge on an ion im a gas, w its velocity when 
acted on by a force of one volt per centimetre, K the rate of 
diffusion of ions in the gas, it can be shown that 
bs 501 Oia 
N x e= 4a; 
This formula is derived from the kinetic theory of gases by 
very simple considerations, it does not involve any assump- 
tion as to the distributions of the velocities of translation of 
the molecules, or the law of force between molecules during 
a collision. It may therefore be considered very reliable 
from a theoretical point of view. 
The values of K and w have been found experimentally in 
a large number of cases, so that the values of N xe may be 
calculated. The mean values of wu for positive and negative 
ions produced by Rontgen rays in different gases have been 
found by Prof. Rutherford *. Another set of determinations 
of the velocities have been made by Prof. Zeleny Tf, using a 
different method in which the velocities of the positive and 
negative ions have been determined separately. 
The values of u for ions produced by ultra-violet light have 
also been determined by Prof. Rutherford f. 
The values of K have been determined by the author for 
ions produced by R6ntgen rays, ultra-violet light, and radio- 
active substances §. 
Taking the values of uw given by Prof. Rutherford, the 
following values of N xe are obtained, for ions produced by 
Réntgen rays :— 
Air. &) 36 Se) sb JO 
Oey gn 2 cen Re Za hOR? 
Carbonic Acid . . 1°30 10—” 
HMydropen .....3)a0i)4-07, 105° 
E. Rutherford, Phil. Mag. November 1897. 
+ J. Zeleny, Phil. Trans. vol. exev. pp. 198-234 (1900). 
E. Rutherford, Cambridge Philosophical Society Proc. vol. ix. 
pt. viii. (1898). 
§ J. S. Townsend, Phil. Trans. vol. exciii. (1899) and vol. exev. 
