
CHAPTER II. 
IONIZATION THEORY OF GASES. 
25. lIonization of gases by radiation. The most important 
property possessed by the radiations from radio-active bodies is 
their power of discharging bodies whether positively or negatively 
electrified. As this property has been made the basis of a method 
for an accurate quantitative analysis and comparison of the 
radiations, the variation of the rate of discharge under different 
conditions and the processes underlying it will be considered in 
some detail. 
In order to explain the similar discharging power of Rontgen 
rays, the theory’ has been put Earth 
forward that the rays pro- _ / nee 
duce positively and negatively 
charged carriers throughout # 
the volume of the gas sur- ¥ 
rounding the charged body, and ee ae 
that the rate of production 1s die “ 
proportional to the intensity za oN 
of the radiation. These carriers, Fig. 1. 
or ions? as they have been termed, move with a uniform velocity 
through the gas under a constant electric field, and their velocity 
varies directly as the strength of the field. 
Suppose swe have a gas between two metal plates A and B 
(Fig. 1) exposed to the radiation, and that the plates are kept 
at a constant difference of potential. A definite number of ions 
will be produced per second by the radiation, and the number 
1 J. J. Thomson and Rutherford, Phil. Mag. Nov. 1896. 
2 The word ion has now been generally adopted in the literature of the 
subject. In the use of this word no assumption is made that the ions in gases 
are the same as the corresponding ions in the electrolysis of solutions. 
