﻿884 
  Messrs. 
  T. 
  H. 
  Laby 
  and 
  G. 
  W. 
  C. 
  Kaye 
  on 
  

  

  Ionization 
  and 
  Pressure. 
  — 
  Figs 
  3, 
  4, 
  and 
  5 
  (PL 
  XXVT.) 
  

   show 
  the 
  relation 
  between 
  ionization 
  and 
  pressure 
  for 
  the 
  

   gases 
  hydrogen, 
  air, 
  and 
  carbon 
  dioxide 
  over 
  the 
  range 
  1 
  to 
  

   ]7 
  atmospheres, 
  the 
  unit 
  of 
  ionization 
  being 
  an 
  arbitrary 
  one 
  

   for 
  each 
  curve. 
  

  

  It 
  will 
  be 
  noticed 
  that, 
  for 
  hydrogen 
  at 
  the 
  lower 
  pressures 
  

   the 
  graph 
  is 
  almost 
  a 
  straight 
  line, 
  and 
  becomes 
  only 
  slightly 
  

   bent 
  at 
  the 
  highest 
  pressures. 
  The 
  corresponding 
  curve 
  lot- 
  

   ah- 
  (fig. 
  4) 
  show- 
  a 
  resemblance 
  to 
  that 
  of 
  hydrogen, 
  though 
  

   the 
  curvature 
  of 
  the 
  former 
  is 
  a 
  little 
  more 
  pronounced. 
  

   In 
  fiff. 
  5 
  we 
  have 
  a 
  similar 
  curve 
  for 
  carbon 
  dioxide 
  but 
  with 
  

  

  o 
  

  

  a 
  curvature 
  much 
  more 
  marked. 
  

  

  The 
  readings 
  connecting 
  ionization 
  with 
  pressure 
  1 
  are 
  

   indicated 
  in 
  fig. 
  5 
  for 
  two 
  positions 
  of 
  the 
  radium* 
  

  

  (1) 
  The 
  dots 
  (from 
  which 
  the 
  graph 
  is 
  drawn) 
  denote 
  

   reading- 
  obtained 
  when 
  the 
  7 
  rays 
  entered 
  the 
  vessel 
  through 
  

   its 
  aluminium 
  end-. 
  

  

  (2) 
  Tie- 
  crosses 
  are 
  the 
  readings 
  when 
  the 
  7 
  rays 
  entered 
  

   the 
  vessel 
  through 
  its 
  brass 
  -ides. 
  A 
  line 
  through 
  the 
  crosses 
  

   would 
  be 
  -lightly 
  more 
  curved 
  than 
  the 
  one 
  drawn. 
  According 
  

   to 
  the 
  interpretation 
  given 
  later, 
  this 
  would 
  show 
  that 
  the 
  

   secondary 
  radiation 
  from 
  brass 
  i- 
  much 
  the 
  same 
  as 
  from 
  

   aluminium. 
  

  

  The 
  graphs 
  of 
  figs. 
  3, 
  i. 
  & 
  5 
  are 
  reduced 
  in 
  fig. 
  G 
  to 
  the 
  

   sane- 
  coordinate- 
  lor 
  each 
  gas 
  ; 
  to 
  do 
  this 
  we 
  determined 
  

   the 
  relative 
  ionization 
  in 
  our 
  apparatus 
  of 
  the 
  three 
  gases 
  

   when 
  ai 
  atmospheric 
  pressure. 
  In 
  curves 
  A, 
  B, 
  C 
  of 
  that 
  

   figure 
  ionization 
  is 
  plotted 
  against 
  density, 
  the 
  density 
  of 
  

   hydrogen 
  at 
  17° 
  and 
  760 
  mm. 
  being 
  taken 
  as 
  unity. 
  

  

  In 
  the 
  case 
  of 
  air 
  and 
  hydrogen 
  the 
  curves 
  (D 
  and 
  E) 
  are 
  

   ionization-pressure 
  curves; 
  to 
  the 
  corresponding 
  graph 
  C 
  for 
  

   C0 
  a 
  a 
  correction 
  has 
  been 
  applied 
  to 
  allow 
  for 
  the 
  deviation 
  

   cf 
  this 
  gas 
  from 
  Boyle's 
  law 
  : 
  Regnault's 
  results 
  have 
  been 
  

   used 
  to 
  make 
  the 
  correction. 
  It 
  should 
  be 
  noticed 
  that 
  the 
  

   lengths 
  which 
  the 
  curves 
  C, 
  D, 
  and 
  E 
  (fig. 
  C>) 
  cut 
  off 
  from 
  any 
  

   ordinate 
  give 
  the 
  relative 
  ionization 
  in 
  the 
  three 
  gases 
  when 
  

   their 
  relative 
  densities 
  are 
  as 
  their 
  molecular 
  weights, 
  namely, 
  

   44, 
  28"4, 
  and 
  2. 
  For 
  convenience 
  we 
  shall 
  refer 
  to 
  C, 
  D, 
  and 
  

   E 
  as 
  press 
  ure-ionization 
  curves. 
  

  

  Xo 
  correction 
  was 
  made 
  for 
  the 
  deviation 
  of 
  air 
  from 
  the 
  

   gas 
  laws, 
  for 
  the 
  readings 
  of 
  an 
  air-manometer 
  give 
  exactly 
  

   the 
  corresponding 
  densities 
  of 
  air 
  in 
  the 
  apparatus 
  ; 
  no 
  

   correction 
  was 
  applied 
  in 
  the 
  case 
  of 
  hydrogen. 
  

  

  The 
  curve 
  C 
  represents 
  carbon 
  dioxide 
  on 
  both 
  the 
  systems 
  

   of 
  coordinates 
  of 
  fig. 
  6, 
  

  

  