﻿Active 
  Deposit 
  of 
  Actinium 
  in 
  Electric 
  Fields. 
  391 
  

  

  and 
  Bronson 
  * 
  for 
  the 
  active 
  deposit 
  of 
  radium, 
  using 
  low 
  

   voltages. 
  They 
  did 
  not 
  detect 
  any 
  appreciable 
  effect, 
  how- 
  

   over, 
  using 
  larger 
  potential 
  differences. 
  This 
  is 
  possibly 
  due 
  

   to 
  the 
  relative 
  weakness 
  of 
  the 
  ionization 
  produced 
  by 
  

   Rontgen 
  rays 
  — 
  the 
  external 
  source 
  of 
  ionization 
  which 
  they 
  

   ■employed. 
  The 
  increase 
  in 
  anode 
  activity 
  must 
  be 
  greater 
  

   for 
  low 
  voltages 
  than 
  for 
  high 
  ones, 
  using 
  the 
  same 
  external 
  

   ionization, 
  since 
  the 
  time 
  during 
  which 
  the 
  charged 
  deposit 
  

   atoms 
  are 
  in 
  the 
  gas 
  is 
  longer 
  in 
  the 
  former 
  case, 
  and 
  hence 
  

   there 
  is 
  a 
  greater 
  facility 
  for 
  recombination 
  to 
  occur. 
  

   Experimenting 
  with 
  actinium 
  D, 
  Kovarik 
  f 
  found 
  a 
  very 
  

   marked 
  recombination 
  effect 
  even 
  with 
  relatively 
  high 
  

   voltages. 
  Employing 
  two 
  plates 
  12'3 
  mm. 
  apart 
  and 
  a 
  

   potential 
  difference 
  of 
  115 
  volts, 
  which 
  was 
  sufficient 
  to 
  

   produce 
  an 
  approximate 
  saturation 
  of 
  the 
  currents 
  due 
  to 
  the 
  

   radiations 
  from 
  the 
  active 
  deposits 
  he 
  employed, 
  he 
  showed 
  

   that 
  with 
  a 
  powerful 
  ionizing 
  source 
  the 
  cathode 
  activity 
  

   increased 
  as 
  the 
  amount 
  of 
  ionization 
  decreased. 
  Further 
  

   experiments 
  showing 
  the 
  influence 
  of 
  voltage 
  on 
  the 
  distri- 
  

   bution 
  of 
  the 
  deposit 
  brought 
  out 
  the 
  importance 
  of 
  the 
  

   time 
  factor. 
  

  

  On 
  the 
  theory 
  of 
  recombination 
  it 
  is 
  possible 
  to 
  offer 
  some 
  

   •explanation 
  of 
  the 
  observation 
  of 
  Wellisch 
  and 
  Bronson 
  that 
  

   the 
  percentage 
  anode 
  activity 
  represents 
  the 
  percentage 
  lack 
  

   of 
  saturation 
  of 
  the 
  ionization 
  current 
  passing 
  through 
  the 
  

   gas. 
  They 
  found 
  that 
  " 
  within 
  the 
  limits 
  of 
  experimental 
  

   error, 
  the 
  ratio 
  of 
  the 
  two 
  ionization 
  currents 
  obtained 
  for 
  

   two 
  potentials 
  not 
  too 
  low 
  was, 
  like 
  the 
  percentage 
  cathode 
  

   activity, 
  independent 
  of 
  the 
  amount 
  of 
  the 
  emanation 
  in 
  the 
  

   vessel 
  ; 
  and, 
  moreover, 
  that 
  this 
  ratio 
  was 
  identical 
  with 
  the 
  

   ratio 
  of 
  the 
  percentage 
  cathode 
  activities 
  corresponding 
  to 
  

   these 
  two 
  potentials." 
  The 
  percentage 
  cathode 
  activity 
  

   measures 
  the 
  amount 
  of 
  active 
  deposit 
  which 
  reaches 
  the 
  

   electrode 
  still 
  charged 
  positively. 
  The 
  ionization 
  current 
  is 
  

   a 
  measure 
  of 
  the 
  number 
  of 
  positive 
  ions 
  reaching 
  the 
  same 
  

   electrode. 
  Since 
  these 
  quantities 
  are 
  in 
  the 
  same 
  ratio, 
  it 
  

   indicates 
  that 
  a 
  charged 
  deposit 
  atom 
  has 
  exactly 
  the 
  same 
  

   chance 
  as 
  a 
  positive 
  ion 
  of 
  recombination 
  with 
  a 
  negative 
  

   ion. 
  Although 
  there 
  is 
  no 
  a 
  priori 
  reason 
  why 
  radium 
  should 
  

   behave 
  like 
  actinium, 
  still 
  the 
  hypothesis 
  of 
  recombination 
  

   suggests 
  an 
  explanation 
  for 
  the 
  high 
  anode 
  activity 
  which 
  

   Wellisch 
  and 
  Bronson 
  found 
  at 
  lower 
  pressures. 
  They 
  state 
  

   that 
  a 
  large 
  current 
  due 
  to 
  ionization 
  by 
  collision 
  was 
  passing 
  

   through 
  the 
  gas, 
  during 
  the 
  exposure 
  of 
  the 
  electrodes. 
  In 
  

  

  * 
  Wellisch 
  and 
  Bronson, 
  Phil. 
  Mag. 
  xxiii. 
  p. 
  714 
  (1912). 
  

   t 
  Kovarik, 
  Phil. 
  Mag. 
  xxiv. 
  p. 
  722 
  (1912). 
  

  

  