﻿in Gaseous Mixtures by Rontgen Radiation, 327 



Columns 1, 2, 3, and 4 need no explanation except that 

 partial pressures in column 2 were calculated from the 

 weights in column 1, it being assumed for uniformity that 

 the total pressure was always 76 cm. of mercury. The 

 absorption of Cu X-radiation was taken from 



\,=-OO0U3 d p B + -00327^, 



where p a and p v are the partial pressures expressed in 

 centimetres of mercury. 



Column 5 gives the ionization that would have been 

 produced in the air contained in the gaseous mixture if it 

 had been alone, assuming proportionality with pressure over 

 this small range of pressure. 



Column 6 gives the additional ionization due to the ad- 

 mixture of C 2 H 5 Br with the air, in terms of ionization in air 

 at atmospheric pressure. 



Column 7 gives the ratio 



additional ionization due to admixture of C 2 Ii 5 Br 

 partial pressure of C 2 H 5 Br 



A similar series of experiments was made using the fluor- 

 escent X-radiation from silver (series K). This radiation is 

 a fairly penetrating radiation and produces a much greater 

 ionization in ethyl bromide relative to air than the soft 

 copper radiation of series K. A more delicate test is there- 

 fore possible with the silver radiation. In addition to this, 

 it causes the emission of a well known fluorescent X-radiation 

 from bromine, and an intense accompanying corpuscular 

 radiation, which produce their ionizations in the surrounding 

 gaseous mixture, thus increasing the ionization due to direct 

 action. The ionization due to the fluorescent X-radiation 

 from Br was negligible in these experiments : very little of this 

 radiation was absorbed. There was, however, quite a consider- 

 able correction to be made owing to the corpuscular radiation 

 from the aluminium ends of the ionization-chamber, for silver 

 X-radiation (series K) excites an intense corpuscular radia- 

 tion in aluminium. It will, however, appear from what 

 follows that this corpuscular radiation effect did not appre- 

 ciably affect the relative values. Table IV. gives the results 

 of experiments. 



