Gaseous Mixtures hy Rontgen and Corpuscular Radiations. 835 



radiation. That the corpuscular radiation was totally absorbed 

 by the gas inside the ionization-chamber was shown by finding 

 the relation between ionization and pressure of: the gas in the 

 manner of Beatty *. 



In fig. 2, line A shows the ionization produced by Sn 

 X-radiation (series K) in air at different pressures, when the 



Pig. 2. 



24 28 52 36 40 44 43 52 



fftCSSUP.E CF G*S IN CIV!. OF MERCU1Y. 



ends of! the ionization-chamber were of carbon, assuming 

 the ionization to be proportional to the pressure. Such a 

 relation would of course hold only if the ends were of air; 

 with carbon ends the curve is actually concave upwards, but 

 the ionization is so small in comparison with that due to the 

 corpuscular radiation, that the error in assuming proportion- 

 ality is negligible. In the apparatus we used, the deviation was 

 too small to be readily measured. Curve B shows the rela- 

 tionship between ionization and pressure when the ends were 

 of o-old. Subtracting the ordinates of curve A from the corre- 

 sponding ordinates of curve B gives the ordinates of curve C, 

 which thus represents the relation between the ionization 

 produced by a corpuscular radiation in the air and the 

 pressure of the air, — the corpuscular radiation being the 

 difference between the corpuscular radiations from gold and 

 carbon, excited by the X-radiation of series K characteristic 

 of tin. 



Similar experiments were performed with ethyl bromide 

 and methyl iodide vapours in the ionization-chamber. The 

 * Proc. Roy. Soc. A.lxxxv. p. 358 (1911). 



