﻿Active 
  Deposit 
  of 
  Radium 
  in 
  an 
  Electric 
  Field. 
  627 
  

  

  taken 
  to 
  dry 
  the 
  gas 
  with 
  which 
  the 
  emanation 
  was 
  mixed. 
  

   This 
  was 
  done 
  by 
  passing 
  the 
  gas 
  through 
  several 
  tubes 
  con- 
  

   taining 
  P 
  2 
  5 
  and 
  glass-wool 
  before 
  it 
  entered 
  the 
  testing 
  

   vessel. 
  

  

  The 
  following 
  table 
  gives 
  the 
  values 
  obtained 
  for 
  the 
  

   cathode 
  deposit 
  expressed 
  as 
  a 
  percentage 
  of 
  the 
  total 
  deposit 
  

   when 
  the 
  emanation 
  was 
  mixed 
  with 
  dried 
  air 
  at 
  pressures 
  of 
  

   210 
  mm. 
  and 
  760 
  mm., 
  and 
  various 
  positive 
  potentials 
  were 
  

   applied 
  to 
  the 
  case 
  : 
  — 
  

  

  These 
  values 
  have 
  been 
  corrected 
  for 
  the 
  amount 
  of 
  un- 
  

   charged 
  deposit 
  that 
  diffuses 
  to 
  the 
  cathode 
  during 
  the 
  

   exposure; 
  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 
  carriers 
  of 
  activity 
  expressed 
  as 
  a 
  per- 
  

   centage 
  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 
  deter- 
  

   minations 
  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 
  connexion, 
  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 
  

   potentials 
  was 
  identical 
  with 
  the 
  ratio 
  of 
  the 
  corresponding 
  

  

  