﻿Active 
  Deposit 
  of 
  Actinium 
  in 
  Electric 
  Fields. 
  383 
  

  

  obviously 
  necessary 
  to 
  eliminate 
  "old" 
  deposit 
  before 
  em- 
  

   ploying 
  electric 
  fields. 
  On 
  this 
  account 
  it 
  is 
  undesirable 
  to 
  

   allow 
  the 
  emanation 
  to 
  diffuse 
  directly 
  from 
  the 
  actinium 
  

   preparation 
  into 
  the 
  field, 
  because 
  under 
  these 
  circumstances 
  

   a 
  mixture 
  of 
  emanation 
  and 
  all 
  the 
  subsequent 
  products, 
  

   charged 
  and 
  uncharged, 
  in 
  unknown 
  proportions, 
  is 
  entering 
  

   the 
  field. 
  Changes 
  in 
  the 
  strength 
  of 
  the 
  electric 
  field 
  and 
  

   in 
  the 
  pressure 
  of 
  the 
  gas 
  into 
  which 
  diffusion 
  is 
  occurring 
  

   are 
  bound 
  to 
  alter 
  the 
  proportions 
  of 
  the 
  products, 
  and 
  

   consequently 
  mask 
  the 
  true 
  effects. 
  Neglect 
  of 
  special 
  pre- 
  

   cautions 
  to 
  eliminate 
  this 
  source 
  of 
  error 
  is 
  probably 
  responsible 
  

   for 
  some 
  of 
  the 
  discrepancies 
  between 
  the 
  results 
  obtained 
  by 
  

   the 
  earlier 
  investigators. 
  

  

  I. 
  

  

  The 
  first 
  experiment 
  was 
  designed 
  to 
  test 
  whether, 
  in 
  a 
  

  

  given 
  electric 
  field, 
  the 
  ratio 
  of 
  the 
  anode 
  activity 
  to 
  that 
  of 
  

  

  the 
  cathode 
  was 
  a 
  function 
  of 
  the 
  quantity 
  of 
  emanation 
  

  

  employed. 
  A 
  long 
  brass 
  tube 
  AB 
  (fig. 
  2) 
  carrying 
  a 
  short 
  

  

  Fig. 
  2. 
  

  

  side-tube 
  C 
  was 
  used. 
  Through 
  the 
  centre 
  of 
  AB 
  passed 
  a 
  

   copper 
  wire 
  DE 
  on 
  which 
  the 
  active 
  deposit 
  could 
  be 
  col- 
  

   lected. 
  This 
  was 
  supported 
  at 
  A 
  and 
  B 
  by 
  ebonite 
  stoppers. 
  

   The 
  electric 
  field 
  was 
  produced 
  by 
  earthing 
  AB 
  and 
  charging 
  

   the 
  wire 
  to 
  a 
  positive 
  or 
  negative 
  potential 
  by 
  means 
  of 
  a 
  

   battery 
  of 
  small 
  accumulators. 
  The 
  emanation 
  was 
  carried 
  

   into 
  AB 
  by 
  a 
  steady 
  current 
  of 
  air, 
  through 
  the 
  small 
  orifice 
  

   in 
  the 
  side-tube, 
  and 
  was 
  freed 
  from 
  dust 
  and 
  active 
  

   deposit 
  by 
  cotton-wool 
  which 
  was 
  packed 
  tightly 
  in 
  C. 
  The 
  

   flow 
  of 
  air 
  was 
  produced 
  by 
  means 
  of 
  two 
  aspirators, 
  and 
  

   the 
  rate 
  of 
  flow 
  was 
  adjusted 
  so 
  that 
  no 
  measurable 
  activity 
  

   was 
  found 
  on 
  the 
  last 
  few 
  centimetres 
  of 
  the 
  wire. 
  Before 
  

   reaching 
  the 
  actinium 
  preparation, 
  which 
  was 
  contained 
  in 
  a 
  

   wide 
  glass 
  tube, 
  the 
  air 
  was 
  dried 
  by 
  bubbling 
  through 
  

  

  2 
  D2 
  

  

  