﻿532 
  

  

  Mr. 
  A. 
  Fleck 
  on 
  the 
  

  

  when 
  the 
  soft 
  ft 
  rays 
  are 
  operative, 
  the 
  constant 
  value 
  reached 
  

   is 
  relatively 
  much 
  greater. 
  

  

  Uranium 
  X 
  2 
  is 
  also 
  obtained 
  in 
  considerable 
  excess 
  over 
  

   the 
  fraction 
  of 
  uranium 
  X 
  1? 
  which 
  is 
  brought 
  down 
  by 
  pre- 
  

   cipitating 
  lead 
  or 
  bismuth 
  as 
  sulphide 
  in 
  a 
  dilutely 
  acid 
  

   solution 
  of 
  uranium 
  X. 
  

  

  If 
  lead 
  sulphate 
  is 
  precipitated 
  in 
  an 
  acid 
  solution 
  containing 
  

   uranium 
  X, 
  the 
  curves 
  obtained 
  by 
  measuring 
  the 
  activity 
  of 
  

   the 
  precipitate 
  are 
  shown 
  in 
  fig. 
  2. 
  Curve 
  I. 
  is 
  the 
  theoretical 
  

  

  Fig-. 
  2. 
  

  

  

  Z) 
  

  

  I- 
  Theorcfc? 
  

   -froM 
  J- 
  1- 
  It 
  

  

  -At, 
  

  

  

  ffi-Xx/xnn 
  

   PlS0 
  4 
  ttr 
  

   o| 
  AW™,-*, 
  

  

  \~t 
  

  

  CM 
  

  

  hCini 
  Cu.fJ'e 
  jtQ>n 
  

   §W 
  I 
  w. 
  f\\ 
  

  

  enfc! 
  Co^v«/e 
  

  

  h 
  O0O3h 
  n,i 
  

  

  curve 
  calculated 
  on 
  the 
  assumptions 
  that 
  the 
  rays 
  of 
  

   uranium 
  X 
  : 
  , 
  if 
  any, 
  do 
  not 
  reach 
  the 
  ionizing-chamber 
  of 
  the 
  

   electroscope, 
  and 
  that 
  it 
  disintegrates 
  directly 
  into 
  uranium 
  X 
  2 
  , 
  

   which 
  does 
  give 
  rays 
  penetrating 
  into 
  the 
  electroscope, 
  and 
  

   which 
  has 
  a 
  period 
  of 
  average 
  life 
  of 
  1*6 
  minutes. 
  Curve 
  II. 
  

   is 
  the 
  curve 
  obtained 
  experimentally 
  by 
  precipitating 
  lead 
  

   sulphate 
  in 
  a 
  uranium 
  X 
  solution 
  and 
  measuring 
  the 
  activity 
  of 
  

   the 
  product 
  through 
  O'l 
  mm. 
  of 
  aluminium, 
  that 
  is 
  to 
  say, 
  hard 
  

   fi 
  rays 
  alone 
  are 
  measured. 
  This 
  curve 
  is 
  seen 
  to 
  be 
  in 
  close 
  

   agreement 
  with 
  the 
  theoretical 
  curve. 
  It 
  is 
  therefore 
  con- 
  

   cluded 
  that 
  the 
  hard 
  /3 
  rays 
  usually 
  associated 
  with 
  uranium 
  X 
  

   do 
  not 
  belong 
  to 
  the 
  body 
  with 
  a 
  half 
  period 
  of 
  2<k'6 
  days, 
  

   but 
  to 
  the 
  new 
  body 
  of 
  half 
  period 
  of 
  1*1 
  minutes. 
  Curve 
  III. 
  

   is 
  the 
  curve 
  obtained 
  by 
  precipitating 
  lead 
  sulphate 
  in 
  the 
  

   usual 
  way 
  and 
  measuring 
  the 
  activity 
  of 
  the 
  precipitate 
  

  

  