252 Taylor — Ionization of Different Gases by the 



the ionization produced at any point in the path of the particle 

 is proportional to the energy consumed, Geiger* has shown that 

 the ionization / at any point in the path is given by the rela- 

 tion 



1 = 



(r-x) 



where c and r are constants and x is the distance from the 

 source of rays. By comparing this theoretical ionization 

 curve with the experimental curve obtained in hydrogen for a 

 pencil of rays, Geiger found the two to agree very closely. 



This theoretical curve has been compared with the experi- 

 mental curves obtained in each of the gases and vapors given 

 in Table I and a very close agreement between theoretical 

 and experimental curves was found for each gas. To make 

 this comparison, it was necessary to determine the constants r 

 and c for each gas. For the value of r, Geiger used the aver- 

 age range of the alpha particles in the pencil of rays. Since 

 the maximum range of the alpha particles in the cone of rays 

 used in the present experiments was always 11 - 1 centimeters, 

 the average range of the alpha particles in this cone of rays 

 emerging from the cylinder containing the polonium was 

 slightly less than 11*1 centimeters. Consequently 10"8 centi- 

 meters were taken as the value of the average range of the 

 alpha particle, that is, 10*8 centimeters are supposed to repre- 

 sent the average distance the alpha particles traveled in each 

 gas before losing their power of producing ions. In order to 

 determine c for any one gas, the ionization (ordinate of the 

 ionization curve figures 1, 2, and 3) and the corresponding dis- 

 tance x of the source of rays from the ionization chamber 

 (abscissa of curve) were substituted in the equation 



1= 



(10-8— x)X 



and the equation solved for c. Separate values of c were thus 

 obtained for various distances of the source of rays from the 

 ionization chamber between x = and 9*5 centimeters, and 

 the mean value of these separate determinations found for 

 each gas. The mean values of e as found in the above man- 

 ner for all the gases and vapors used are recorded in column 

 2, Table I. 



* Proc. Royal Society, Series A, vol. Ixxxiii, No. A 565, p. 505. 



