Cases of Ionization hy X-Rays. 379 



Assuming the absorption of tlie corpuscular radiation to be 

 dependent simply on the quantity of matter passed through, 

 Ex becomes '3 approximately. 



For /i we will take the value found by Mr. Sadler, J, as 

 approximately correct. 



n 



' 1 



therefore = 3 x 1/6 X &-=■ X 8*8 x , 3 = 1*7 approximately. 

 n I'D 



We should thus conclude that the ratio of ionization due to 

 ethyl bromide to ionization in air at the same pressure would, 

 owing to the emission of corpuscular radiation, increase from 30 

 to about 80 when using the homogeneous radiation from silver. 

 From column -i of Table I. it will be seen that the increase 

 observed in the ionization produced in ethyl bromide when 

 the ionizing X-radiation was made more penetrating than the 

 secondary X-radiation characteristic of bromine was from 

 about 30 to 153 for the radiation from silver. Thus quite a 

 considerable portion of the observed increase might be attri- 

 buted to the corpuscular radiation. The exact proportion 

 cannot be given with certainty. 



On the other hand, Mr. Crowther *, from a study of the 

 ionization in ethyl bromide at low pressures, concludes that 

 no appreciable portion of the ionization is due to very soft 

 secondary radiations, such as these corpuscular radiations. 



It should be observed that we have assumed that the emission 

 of corpuscular radiation is not affected by the state of the 

 bromine, that is, that the corpuscular radiation is an atomic 

 phenomenon simply. Further experiments are being made 

 by the writer to test these conclusions. 



The results of experiments may be briefly stated thus : — 

 From the results of observations on ionizaion in many 

 gases and. vapours complete regularity in behaviour has been 

 found. It is necessary and sufficient to know the penetrating 

 power of the characteristic secondary X-radiations emitted 

 by the constituent elements to determine the way in which 

 the ionization in a gas or vapour varies wiih the penetrating- 

 power of the ionizing radiation. (See fig. 2.) In other 

 words, it is necessary and sufficient to know the X-ray line 

 spectra for the constituent elements. No anomalous ionization 

 by X-rays has been observed. 



A much fuller account of the experiments will be published 

 later. 



My thanks are due to Mr. G. H. Martyn, B.Sc, for his 

 most valuable assistance throughout the experiments. 



Wheatstone Laboratory, 

 King's College. 



* Hoy. Soc. Proc. A. lxxxii. pp. 103-127. 



