﻿Active 
  Deposit 
  of 
  Radium 
  in 
  an 
  Electric 
  Field. 
  635 
  

  

  noticed 
  that 
  these 
  curves 
  cut 
  the 
  axis 
  of 
  ordinates 
  at 
  the 
  

   points 
  marked 
  '1 
  and 
  A, 
  these 
  points 
  representing 
  respec- 
  

   tive^ 
  66 
  per 
  cent. 
  of 
  the 
  total 
  number 
  of 
  positive 
  ions 
  and 
  

   38 
  per 
  cent, 
  of 
  the 
  total 
  number 
  of 
  positively 
  charged 
  deposit 
  

   particles. 
  This 
  type 
  of 
  curve 
  has 
  already 
  been 
  treated 
  by 
  

   Wellisch 
  and 
  Woodrow 
  * 
  for 
  the 
  case 
  of 
  the 
  columnar 
  re- 
  

   combination 
  resulting 
  from 
  a-particle 
  ionization. 
  It 
  was 
  

   shown 
  by 
  them 
  that 
  the 
  ordinate 
  of 
  the 
  point 
  of 
  intersection 
  

   represents 
  the 
  fraction 
  of 
  the 
  total 
  number 
  of 
  ions 
  which 
  

   escapes 
  from 
  the 
  a-particle 
  column 
  as 
  a 
  result 
  of 
  molecular 
  

   agitation 
  and 
  diffusion. 
  Inasmuch 
  as 
  volume 
  recombination 
  

   is 
  absent, 
  these 
  ions 
  are 
  brought 
  over 
  to 
  the 
  electrodes 
  by 
  a 
  

   very 
  small 
  electric 
  field. 
  If 
  we 
  draw 
  through 
  the 
  point 
  of 
  

   intersection 
  a 
  straight 
  line 
  parallel 
  to 
  the 
  axis 
  of 
  potential, 
  

   and 
  if 
  we 
  refer 
  the 
  curve 
  to 
  this 
  straight 
  line 
  as 
  a 
  new 
  axis 
  

   of 
  potential, 
  then 
  the 
  new 
  ordinates 
  will 
  indicate 
  to 
  what 
  

   extent 
  the 
  electric 
  potential 
  is 
  effective 
  in 
  preventing 
  recom- 
  

   bination 
  between 
  those 
  ions 
  which 
  still 
  remain 
  in 
  the 
  column 
  

   after 
  the 
  initial 
  diffusion 
  has 
  occurred. 
  If 
  we 
  treat 
  the 
  

   curves 
  of 
  fig. 
  3 
  in 
  a 
  similar 
  manner 
  we 
  see 
  that, 
  whereas 
  in 
  

   the 
  vessel 
  employed 
  66 
  per 
  cent, 
  of 
  the 
  positive 
  ions 
  on 
  the 
  

   average 
  escaped 
  from 
  the 
  a-particle 
  column, 
  the 
  corresponding 
  

   figure 
  for 
  the 
  positively 
  charged 
  recoil 
  atoms 
  was 
  only 
  38 
  

   per 
  cent. 
  This 
  slowness 
  with 
  which 
  the 
  recoil 
  atoms 
  diffuse 
  

   is 
  readily 
  ascribable 
  to 
  their 
  relatively 
  large 
  size 
  and 
  mass. 
  

   Of 
  those 
  ions 
  and 
  recoil 
  atoms 
  which 
  do 
  not 
  escape 
  by 
  dif- 
  

   fusion 
  from 
  the 
  column, 
  approximately 
  the 
  same 
  fraction 
  is 
  

   brought 
  over 
  by 
  any 
  given 
  potential 
  ; 
  it 
  seems 
  that 
  there 
  is 
  

   here 
  some 
  compensating 
  influence 
  at 
  work, 
  probably 
  the 
  

   greater 
  tendency 
  of 
  the 
  recoil 
  atoms 
  to 
  recombine 
  with 
  

   negative 
  ions 
  is 
  partly 
  balanced 
  by 
  the 
  smaller 
  number 
  of 
  

   encounters 
  with 
  these 
  ions. 
  

  

  The 
  existence 
  of 
  a 
  definite 
  limiting 
  value 
  to 
  the 
  percentage 
  

   cathode 
  activity 
  has 
  been 
  ascribed 
  above 
  to 
  a 
  continual 
  pro- 
  

   cess 
  of 
  gain 
  and 
  loss 
  of 
  charge 
  which 
  occurs 
  during 
  the 
  

   recoil 
  motion 
  of 
  the 
  active 
  deposit 
  particle. 
  It 
  is 
  to 
  be 
  ex- 
  

   pected 
  that 
  this 
  limiting 
  value 
  will 
  depend 
  upon 
  the 
  nature 
  

   of 
  the 
  gas 
  into 
  which 
  the 
  particle 
  recoils 
  ; 
  the 
  experimental 
  

   determination 
  showed 
  that 
  this 
  was 
  in 
  general 
  the 
  case, 
  

   although 
  the 
  limiting 
  value 
  for 
  hydrogen 
  was 
  within 
  the 
  

   limits 
  of 
  error 
  the 
  same 
  as 
  that 
  for 
  air. 
  The 
  fact 
  that 
  the 
  

   value 
  for 
  ether 
  is 
  as 
  small 
  as 
  10 
  per 
  cent, 
  is 
  surprising, 
  and 
  

   is 
  in 
  all 
  probability 
  to 
  be 
  ascribed 
  to 
  the 
  ease 
  with 
  which 
  the 
  

   molecules 
  of 
  ether 
  are 
  ionized. 
  

  

  * 
  Wellisch 
  and 
  Woodrow, 
  Phil. 
  Mag. 
  Sept. 
  1913. 
  

  

  