﻿330 Prof. Buikla and Mr. Simons on Ionization 



but there was evidently no marked deviation from propor- 

 tionality even ^vitli these. 



It should be pointed out that the total energy absorbed by 

 the gaseous mixtures is not exactly given by the simple 

 formula Ap a + Bp v , where p a and p v denote the partial pres- 

 sures of air and vapour respectively, for the bromine fluor- 

 escent X-radiation (series Kj is absorbed to different extents 

 in the various mixtures. Thus in the dilute mixture between 

 1 and 2 per cent, only of this radiation was absorbed, while 

 in the strongest, about 7 per cent, was probably absorbed. 

 This difference, however, involves quantities of the order of 

 1 per cent, or at most of 2 per cent, of the whole energy 

 absorbed, and is consequently inappreciable. 



The values given in column 7 of Tables IV. and Y. are not 

 on quite the same scale. Those in Table IV. should be 

 divided by (1 — c) and those in Table V. by (1—b) in order 

 to compare them both with the ionization in air at 76 cm. 

 of mercury pressure. From Sadler's results (1 — c) = '7 and 

 (1 — />) = -885. These values then agree very well consider- 

 ing the possible errors involved in the determination of this 

 end effect. 



The constancy of the values in column 7 of Tables III., 

 IV., and V. is remarkable unless quite a large ionization in 

 C 2 H 5 Br is due to the direct action of X-rays, for when the 

 quantity of ethyl bromide is small, the corpuscular radia- 

 tions and even exceedingly soft fluorescent X-radiations are 

 absorbed almost entirely by air ; and when the quantity of 

 ethyl bromide is large, the absorption of these secondary 

 radiations is, in all probability, approximately half in air 

 and half in ethyl bromide. [We may neglect the change 

 of the ionization owing to secondary rays from air being 

 absorbed in ethyl bromide, as this must be very small in the 

 dilute mixtures owing to the small proportion of the rays 

 so absorbed, and in the stronger mixtures owing to the much 

 greater magnitude of the ionizations due to ethyl bromide.] 

 So that the additional ionization due to the addition of ethyl 

 bromide to air was in these experiments closely proportional 

 to the quantity of ethyl bromide, and did not appear to 

 depend to any appreciable extent on whether the secondary 

 rays were absorbed in air or ethyl bromide. But we have 

 found that the ionization in ethyl bromide is about 40 per 

 cent, greater than that in air for the same absorption of 

 X-rays. Kleeman has also concluded that there is greater 

 ionization in ethyl bromide than in air when the corpuscular 

 (electronic) radiation is completely absorbed in both. If, 

 then, all the X-ray ionization had been due to secondary 

 corpuscular radiation we should have expected an increase 



