852 Prof. Barkla and Mr. Philpot : Ionization in Gases and 



ionization in the mixture due to corpuscles from air being- 

 absorbed in C 2 H 5 Br instead of in air itself. 



The corresponding increase in ionization in SH 3 due to 

 mixing a mass m 1 of C 2 H 5 Br with m 2 ' of SH 2 is 



(l-f)c + fc mi ■ f c m * 1,a3 i a m i / l'5~l-33 \ 



s being the ionization in SH 2 alone. 



The ratio of the two expressions above may be equated to 

 the ratio given in column 4, for a particular pressure of 

 C 2 H 5 Br. Assuming / to be unity, that is all the ionization 

 to be due to the corpuscular radiation, the values 1*35, 1 *29, 

 1*25, and 1*20 would be expected in column 4. We have, 

 however, taken no consideration of the fluorescent X-radia- 

 tion of series K which is emitted by the bromine when 

 exposed to such a primary X-radiation, — Ag X-radiation of 

 series K. This Br radiation is of course more completely 

 absorbed by the SH 2 than by the air, and consequently tends 

 to raise the ionizations due to mixing with SH 2 . The eneroy 

 re-emitted by C 2 H 5 Br as fluorescent X-radintion is, however, 

 only about 7 per cent, of the energy absorbed, and of this 

 only about \ was absorbed in SH 2 in these experiments, so that 

 the calculated values should be raised by about 2 per cent., 

 making them 1/37, 1'31, 1'27, 1*22 respectively. The 

 experimentally determined values 1*22, 1*17, 1*20, 1*18 are 

 all somewhat lower, but the first, 1*22, is very unreliable and 

 ought perhaps not to be taken as giving more than the order 

 of magnitude. 



If we used these experiments to determine the fraction of 

 ionization f due to corpuscular radiation, we should obtain 

 the values '53, '73, '85 for the last three — the more accurate 

 determinations. Thus, the most reliable experimental results 

 would lead to the conclusion that something of the order 

 of 75 or 80 per cent, of the ionization in (J 2 H 5 Br by Ag 

 X-radiation of series K is due to the corpuscular radiation. 



(b) Ionization in C 2 H 5 Br, in air, and in mixture of 

 C 2 H 5 Br and air. 



In the second series of experiments on gaseous mixtures 

 we determined the ionizations in (1) a small quantity of 

 ethyl bromide when alone, (2) in air at a much higher 

 pressure, and (3) in the mixture of these two gases at the 

 same partial pressures as when separate. After correction 

 for the absorption of the primary X-radiation in these gases, 

 it was found that the sum of the two first ionizations was 



