﻿Recoil 
  Atoms 
  from 
  Tliorium 
  C 
  and 
  Actinium 
  C. 
  595 
  

  

  phosphorus 
  pentoxide. 
  To 
  ensure 
  the 
  removal 
  of 
  all 
  air, 
  the 
  

   apparatus 
  was 
  filled 
  twice 
  with 
  hydrogen 
  and 
  evacuated. 
  

  

  In 
  this 
  case 
  the 
  form 
  of 
  the 
  curves 
  could 
  be 
  more 
  definitely 
  

   fixed 
  than 
  in 
  the 
  case 
  of 
  air, 
  since 
  a 
  much 
  greater 
  number 
  of 
  

   experimental 
  points 
  could 
  be 
  obtained 
  before 
  the 
  pressure 
  at 
  

   which 
  the 
  recoil 
  atoms 
  were 
  completely 
  stopped 
  was 
  reached. 
  

   It 
  was 
  observed 
  that 
  ionization 
  is 
  produced 
  by 
  recoiling 
  

   atoms 
  up 
  to 
  a 
  pressure 
  of 
  21 
  mm., 
  corresponding 
  to 
  a 
  range 
  

   of 
  *74 
  mm. 
  in 
  hydrogen 
  at 
  atmospheric 
  pressure, 
  i. 
  e. 
  a 
  little 
  

   over 
  four 
  times 
  the 
  range 
  in 
  air. 
  

  

  (b) 
  Recoil 
  from 
  Actinium 
  Active 
  Deposit. 
  

  

  In 
  this 
  case 
  the 
  ionization 
  curves 
  did 
  not 
  show 
  such 
  a 
  

   pronounced 
  "hump" 
  as 
  those 
  obtained 
  for 
  thorium, 
  and 
  

   the 
  curve 
  connecting 
  "ionization 
  per 
  mm. 
  pressure" 
  and 
  

   " 
  pressure 
  " 
  showed 
  only 
  one 
  drop. 
  Fig. 
  5 
  shows 
  a 
  set 
  of 
  

   curves 
  of 
  this 
  character, 
  the 
  experiment 
  in 
  the 
  case 
  shown 
  

   being 
  performed 
  in 
  hydrogen. 
  

  

  Rff. 
  5. 
  

  

  

  

  

  

  

  

  

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  8. 
  12 
  16 
  

  

  PRESS 
  U 
  RE 
  f 
  AIMS.) 
  - 
  

  

  6) 
  

  

  8 
  \l 
  16 
  

  

  Pressure 
  (mms.) 
  — 
  

  

  ZQ 
  

  

  It 
  will 
  be 
  seen 
  that 
  the 
  form 
  of 
  the 
  curve 
  C, 
  unlike 
  that 
  

   of 
  the 
  thorium 
  curve, 
  is 
  almost 
  identical 
  with 
  the 
  main 
  

   portion 
  of 
  the 
  curve 
  shown 
  in 
  fig. 
  2. 
  

  

  In 
  the 
  case 
  of 
  recoil 
  from 
  actinium 
  C 
  the 
  pressure 
  at 
  which 
  

   the 
  recoil 
  atoms 
  cease 
  to 
  reach 
  the 
  ionization 
  chamber 
  was 
  

  

  