﻿in Gaseous Mixtures by Rontgen Radiation. 325 



Later experiments by Mr. Philpot give the ratio of ion- 

 ization by the total absorption of corpuscular radiation in 

 SH 2 and S0 2 as 1*35 ; while for equal absorptions of Ag 

 X-rays the ratio of ionizations is 1*34. 



Many experiments remain to be done with homogeneous 

 X-rays of other penetrating powers, bat these results show 

 conclusively that equal absorptions of corpuscular (electronic) 

 rays and any secondary rays due to them are accompanied by 

 unequal ionizations, and that ionization by corpuscular radia- 

 tion is not atomic. They also show a close connexion, sug- 

 gesting an absolute equality, between the relative ionizations 

 by X-rays and by their corpuscular (electronic) rays., 



(1) Mixtures of air and ethyl bromide in varying proportion. 



Ethyl bromide, when subject to Rontgen radiation, is 

 ionized to a much greater extent than light gases at the same 

 pressure and temperature owing to the presence of a con- 

 stituent element bromine of comparatively high atomic weight. 



Owing to this high ionization it is possible to measure 

 with considerable accuracy the change in the ionization due 

 to the admixture of \ery small quantities of ethyl bromide 

 with air. . 



In order to obtain the mixture of ethyl bromide and air, 

 a small measured quantity of pure liquid ethyl bromide was 

 introduced through a glass tap into a large closed glass 

 vessel of about 6£ litres capacity, and was allowed to evaporate. 

 After complete evaporation of the liquid, the additional 

 partial pressure of the vapour was observed on an attached 

 manometer. Air was then pumped into the vessel till a 

 pressure of about two atmospheres was reached as indicated 

 by the manometer, when the original temperature was 

 approximately attained. The weights and partial pressures 

 of air and ethyl bromide in the vessel were thus known. 

 Tiie mixture was afterwards allowed to pass slowlv from 

 this vessel through the ionization-chamber where the pressure 

 was atmospheric. The partial pressures of air and ethvl 

 bromide in the vessel were then approximately proportional 

 to those in the gas chamber. 



The homogeneous X-radiation first used was the fluorescent 

 radiation from copper giving the spectral line of series K. 

 The corpuscular radiation excited by this in the aluminium 

 window and back of the ionization vessel, in this case 

 3*5 centimetres long, produced ionizations negligible in 

 comparison with the direct ionization of the gas, or at any 

 rate the effect of the ends due to loss or gain of secondary 



