Particles by Homogeneous Rontgen Radiations. 327 



Relative ionization in air and hydrogen due to 

 homogeneous radiations. 



The ionization in hydrogen due to soft radiations is so small 

 that the straight portions of the hydrogen curves in figs. 4 

 and 5 are almost horizontal. A separate set of experiments 

 was made to determine this ionization accurately. The 

 silver leaf was removed from the ionization vessel and the 

 disk electrode replaced by an aluminium wire bent into the 

 form of a ring. A paper strip was wound round the wire to 

 stop cathode radiation from it. The whole volume of the 

 vessel was thus utilized. It is not sufficient to fill the vessel 

 with air and hydrogen alternately, as the small amount of 

 cathode ionization from the paper and cardboard lining would 

 introduce an effect which would increase the value obtained 

 for the direct ionization of the gas. Accordingly the 

 ionization was measured at different pressures, as in the 

 former experiments, and the ratio of the slopes of the linear 

 parts of the curves obtained when the vessel contained air 

 and hydrogen successively gave the ratios of the ionization 

 in these two gases for each radiation, the gases being supposed 

 to be at the same temperature and pressure. 



Table IV. 



Radiator. 



Fe. 



Cu. 



Zn. 



As. 



Sn. 



Ionization in Air 



175-2 



1745 



175-4 



174-6 



25-0 



Ionization in H., 



The relative ionizations of air and hydrogen by primary 

 radiations have been measured by Crowther *. His results 

 are given in the following table. 



r 



rABLE V. 



(aftei 



• Crowther) 



• 







Equivalent spark- 

 gap of bulb. 



8 - 



12 



14 



16 



13 



20 



24 



28 

 5-56 



Ionization in Air 

 Ionization in Ho 



100 



77 



47 -G 



14-7 



9-35 



7-41 



6-58 



It will be seen that in Table IV. softer radiations were 

 used than could have emerged from the bulb in Crowther's 



* J. A. Crowther, Roy. Soc. Proc. ser. A. lxxxii. March 10, 1909. 



