﻿Gaseous 
  Ionization 
  and 
  Pressure. 
  

  

  885 
  

  

  Discussion 
  of 
  Results. 
  

  

  It 
  will 
  be 
  seen 
  from 
  the 
  density-ionization 
  curves 
  (B 
  and 
  C, 
  

   fig. 
  6) 
  that 
  the 
  amount 
  of 
  ionization 
  in 
  carbon 
  dioxide 
  relative 
  

   to 
  air 
  decreases 
  regularly 
  with 
  increasing 
  density. 
  

  

  All 
  the 
  curves 
  in 
  fig. 
  6 
  are 
  convex 
  to 
  the 
  ionization 
  axis 
  

   with 
  curvatures 
  which 
  increase 
  in 
  the 
  order, 
  hydrogen, 
  air, 
  

   carbon 
  dioxide. 
  

  

  At 
  any 
  given 
  pressure 
  employed 
  in 
  these 
  experiments, 
  the 
  

   ionization 
  in 
  carbon 
  dioxide 
  is 
  greater 
  than 
  that 
  in 
  air, 
  but 
  

   as 
  the 
  pressure 
  increases, 
  this 
  difference 
  diminishes, 
  and 
  in 
  

   the 
  apparatus 
  used, 
  the 
  curves 
  indicate 
  that 
  at 
  about 
  33 
  

   atmospheres 
  the 
  ionization 
  would 
  be 
  the 
  same 
  for 
  both 
  gases. 
  

  

  Gas 
  Pressure 
  and 
  Ionization. 
  

  

  To 
  understand 
  these 
  curves, 
  let 
  us 
  consider 
  the 
  nature 
  of 
  

   the 
  radiation 
  to 
  which 
  the 
  gases 
  were 
  subjected. 
  

  

  

  Fig 
  

  

  .7. 
  

  

  

  / 
  

  

  A 
  

  

  1 
  

  

  

  

  

  B 
  

  

  \ 
  

  

  C 
  

  

  \ 
  

  

  There 
  are 
  two 
  classes 
  of 
  radiation 
  present 
  : 
  — 
  

  

  (1) 
  The 
  incident 
  y 
  radiation 
  of 
  a 
  very 
  penetrating 
  nature* 
  

  

  together 
  with 
  any 
  secondary 
  y 
  rays 
  from 
  the 
  gas 
  

   and 
  the 
  walls 
  of 
  the 
  vessel. 
  

  

  (2) 
  The 
  secondary 
  ft 
  radiation 
  produced 
  from 
  the 
  gas 
  and 
  

  

  the 
  walls 
  of 
  the 
  vessel 
  by 
  the 
  original 
  y 
  rays. 
  

  

  (1) 
  The 
  ionization 
  arising 
  from 
  the 
  very 
  penetrating 
  7 
  rays 
  

   forms 
  a 
  small 
  proportion 
  of 
  the 
  whole 
  ionization, 
  and 
  is 
  

  

  * 
  X 
  for 
  Al 
  about 
  -08. 
  McClelland, 
  Trans. 
  Roy. 
  Dubl. 
  Soc. 
  viii. 
  p. 
  107, 
  

   July 
  1904. 
  

  

  