﻿of 
  Radium 
  in 
  an 
  Electric 
  Field. 
  

  

  319 
  

  

  Potential 
  in 
  Volts 
  

  

  Percentage 
  Cathode 
  Activity 
  

  

  

  Air 
  at 
  210 
  mm. 
  

  

  Air 
  at 
  760 
  mm. 
  

  

  20 
  

  

  

  65-3 
  

  

  40 
  

  

  88-7 
  

  

  74-8 
  

  

  160 
  

  

  88-8 
  

  

  83-9 
  

  

  1030 
  

  

  89-2 
  

  

  89-2 
  

  

  2000 
  

  

  88-8 
  

  

  

  

  4000 
  

  

  

  

  89*2 
  

  

  These 
  values 
  have 
  been 
  corrected 
  for 
  the 
  amount 
  of 
  un- 
  

   charged 
  deposit 
  that 
  diffuses 
  to 
  the 
  cathode 
  during 
  the 
  expo- 
  

   sure 
  ; 
  this 
  correction 
  was 
  made 
  by 
  assuming 
  that 
  the 
  uncharged 
  

   deposit 
  particles 
  were 
  distributed 
  on 
  the 
  cathode 
  and 
  the 
  case 
  

   in 
  proportion 
  to 
  the 
  exposed 
  areas, 
  which 
  were 
  as 
  1:50. 
  The 
  

   figures 
  given 
  represent 
  accordingly 
  the 
  number 
  of 
  positive 
  car- 
  

   riers 
  of 
  activity 
  expressed 
  as 
  a 
  percentage 
  of 
  the 
  total 
  number 
  

   of 
  carriers. 
  

  

  In 
  order 
  to 
  demonstrate 
  experimentally 
  that 
  the 
  activity 
  

   which 
  appeared 
  on 
  the 
  anode 
  was 
  almost 
  entirely 
  due 
  to 
  the 
  

   diffusion 
  of 
  uncharged 
  carriers, 
  several 
  experimental 
  determi- 
  

   nations 
  were 
  made 
  of 
  the 
  distribution 
  of 
  the 
  active 
  deposit 
  

   when 
  a 
  large 
  negative 
  potential 
  was 
  applied 
  to 
  the 
  case. 
  As 
  

   an 
  example 
  of 
  the 
  results 
  obtained 
  in 
  this 
  connection 
  it 
  was 
  

   found 
  that 
  when 
  the 
  emanation 
  was 
  mixed 
  with 
  dry 
  air 
  at 
  1 
  

   atmosphere 
  and 
  with 
  a 
  negative 
  potential 
  of 
  160 
  volts, 
  less 
  than 
  

   2 
  per 
  cent 
  of 
  the 
  total 
  deposit 
  appeared 
  on 
  the 
  central 
  electrode 
  

   (anode), 
  showing 
  that 
  no 
  appreciable 
  part 
  of 
  the 
  active 
  carriers 
  

   are 
  negatively 
  charged. 
  

  

  For 
  potentials 
  greater 
  than 
  about 
  40 
  volts 
  the 
  percentage 
  

   cathode 
  activity 
  is 
  independent 
  of 
  the 
  amount 
  of 
  emanation 
  

   employed 
  unless 
  the 
  amount 
  be 
  inordinately 
  large 
  ; 
  over 
  the 
  

   same 
  range 
  of 
  potentials, 
  moreover, 
  it 
  was 
  verified 
  that 
  the 
  

   ratio 
  of 
  the 
  two 
  ionization 
  currents 
  obtained 
  for 
  any 
  two 
  poten- 
  

   tials 
  was 
  identical 
  with 
  the 
  ratio 
  of 
  the 
  corresponding 
  percent- 
  

   age 
  cathode 
  activities. 
  The 
  values 
  obtained 
  for 
  the 
  percentage 
  

   cathode 
  activity 
  for 
  air 
  at 
  210 
  ram 
  pressure 
  are 
  greater 
  than 
  those 
  

   obtained 
  in 
  the 
  previous 
  research 
  ; 
  it 
  is 
  probable 
  that 
  this 
  dis- 
  

   crepancy 
  was 
  due 
  to 
  the 
  fact 
  that 
  in 
  the 
  previous 
  experiment 
  

   some 
  of 
  the 
  ebonite 
  insulation 
  was 
  exposed 
  to 
  the 
  emanation 
  

   so 
  that 
  the 
  central 
  electrode 
  did 
  not 
  receive 
  all 
  the 
  positive 
  

   carriers. 
  The 
  insulation 
  would 
  probably 
  act 
  as 
  a 
  partial 
  con- 
  

   ductor, 
  especially 
  at 
  the 
  lower 
  pressures 
  when 
  it 
  would 
  be 
  

   exposed 
  to 
  the 
  a-radiation 
  proceeding 
  from 
  a 
  considerable 
  dis- 
  

   tance. 
  In 
  the 
  present 
  experiment 
  this 
  source 
  of 
  error 
  was 
  

   carefully 
  avoided, 
  and 
  the 
  result 
  appears 
  to 
  be 
  that 
  the 
  same 
  

  

  