﻿Active 
  Deposit 
  of 
  Actinium 
  in 
  Electric 
  Fields. 
  401 
  

   Integrating, 
  M 
  = 
  C-£'N 
  e~ 
  kt 
  . 
  

  

  Since 
  M 
  = 
  when 
  t 
  = 
  T 
  

  

  and 
  the 
  solution 
  becomes 
  

  

  M 
  = 
  k'lS 
  Q 
  (l-e- 
  kt 
  ). 
  

  

  If 
  the 
  whole 
  of 
  the 
  deposit 
  settles 
  on 
  dust 
  which 
  afterwards 
  

   still 
  retains 
  a 
  negative 
  charge, 
  k' 
  becomes 
  equal 
  to 
  unity. 
  

   In 
  the 
  case 
  given 
  £' 
  = 
  § 
  approximately. 
  

  

  The 
  recombination 
  of 
  the 
  active 
  deposit 
  has 
  apparently 
  

   a 
  half-value 
  period 
  o£ 
  0*77 
  min. 
  This 
  period 
  is 
  unchanged 
  

   when 
  the 
  gas 
  employed 
  is 
  either 
  air, 
  carbon 
  dioxide, 
  or 
  

   hydrogen, 
  showing 
  the 
  effect 
  is 
  purely 
  one 
  of 
  recombination. 
  

   The 
  figs. 
  9 
  and 
  11 
  represent, 
  therefore, 
  two 
  extreme 
  cases 
  

   of 
  the 
  way 
  in 
  which 
  the 
  active 
  deposit 
  may 
  distribute 
  itself. 
  

   All 
  variations 
  of 
  anode 
  and 
  cathode 
  activity 
  are 
  to 
  be 
  ex- 
  

   pected 
  between 
  these 
  limits, 
  when 
  air 
  containing 
  large 
  ions 
  

   or 
  dust 
  particles 
  is 
  employed, 
  and 
  one 
  is 
  in 
  consequence 
  led 
  

   to 
  attribute 
  some 
  of 
  the 
  discrepancies 
  in 
  the 
  early 
  work 
  on 
  

   the 
  subject 
  to 
  this 
  cause. 
  

  

  Summary. 
  

  

  1. 
  It 
  has 
  been 
  shown 
  that 
  the 
  distribution 
  of 
  the 
  active 
  

   deposit 
  of 
  actinium 
  between 
  the 
  electrodes 
  in 
  an 
  electric 
  

   field 
  is 
  independent 
  of 
  the 
  concentration 
  of 
  the 
  emanation. 
  

  

  2. 
  Actinium 
  A 
  has 
  been 
  shown 
  to 
  acquire 
  its 
  positive 
  

   charge 
  in 
  the 
  process 
  of 
  its 
  creation, 
  and 
  in 
  all 
  probability 
  

   the 
  electrical 
  charge 
  of 
  actinium 
  B 
  has 
  the 
  same 
  origin. 
  

  

  3. 
  As 
  regards 
  tbeir 
  electrical 
  properties, 
  both 
  actinium 
  A 
  

   and 
  actinium 
  B 
  behave 
  exactly 
  like 
  the 
  positive 
  ions 
  produced 
  

   by 
  their 
  radiations. 
  They 
  recombine 
  in 
  exactly 
  the 
  same 
  

   way, 
  and 
  the 
  activity 
  collected 
  by 
  the 
  anode 
  in 
  an 
  electric 
  

   field 
  is 
  due 
  solely 
  to 
  deposit 
  atoms 
  which 
  have 
  recombined. 
  

  

  4. 
  Under 
  favourable 
  circumstances 
  recombination 
  con- 
  

   tinues 
  until 
  the 
  whole 
  of 
  the 
  active 
  deposit 
  is 
  electrically 
  

   neutral. 
  

  

  5. 
  The 
  anomalous 
  behaviour 
  previously 
  noticed 
  was 
  pro- 
  

   bably 
  caused 
  by 
  the 
  use 
  of 
  emanation 
  containing 
  active 
  

   deposit, 
  and 
  dust-laden 
  gases. 
  

  

  In 
  conclusion 
  I 
  wish 
  to 
  express 
  my 
  best 
  thanks 
  to 
  Professor 
  

   Rutherford 
  for 
  his 
  kindly 
  interest 
  and 
  advice 
  throughout 
  the 
  

   course 
  of 
  this 
  investigation 
  and 
  for 
  the 
  loan 
  of 
  the 
  large 
  

   preparation 
  of 
  actinium. 
  

  

  The 
  Physical 
  Laboratories, 
  

   The 
  University, 
  Manchester, 
  

   May 
  1,1913. 
  

  

  