﻿Relation 
  hetween 
  Uranium 
  and 
  Radium. 
  853 
  

  

  curve 
  (fig. 
  3) 
  representino- 
  Experiment 
  I. 
  the 
  growth 
  ia 
  

   4 
  years 
  {f=:il&) 
  is 
  about 
  13'3 
  units, 
  or 
  52 
  units 
  per 
  kilogram 
  

   of 
  uranium. 
  The 
  value 
  oi 
  X^ 
  is 
  therefore 
  5*4 
  X 
  10~^ 
  and 
  the 
  

   value 
  of 
  1/X2> 
  the 
  period 
  of 
  average 
  life, 
  is 
  18,500 
  years. 
  

   The 
  lower 
  value 
  (10,000 
  years) 
  given 
  in 
  the 
  preliminary 
  

   communications 
  is 
  solely 
  due 
  to 
  a 
  value 
  having 
  been 
  used 
  

   for 
  the 
  constant 
  of 
  the 
  instrument, 
  which 
  is 
  subject 
  to 
  three 
  

   corrections 
  all 
  operating 
  in 
  the 
  same 
  direction: 
  (1) 
  the 
  effect 
  

   of 
  keeping 
  the 
  leaf 
  charged, 
  (2) 
  the 
  effect 
  of 
  altering 
  the 
  

   position 
  of 
  the 
  charging 
  rod, 
  and 
  (3) 
  the 
  alteration 
  in 
  the 
  

   value 
  of 
  the 
  ratio 
  between 
  U 
  and 
  Ra 
  in 
  pitchblende. 
  

  

  In 
  Experiment 
  lY. 
  the 
  value 
  depends 
  entirely 
  on 
  the 
  

   initial 
  observation 
  to 
  which, 
  as 
  already 
  mentioned, 
  not 
  much 
  

   weight 
  can 
  be 
  attached. 
  The 
  experiment 
  shows 
  for 
  the 
  first 
  

   three 
  years 
  a 
  growth 
  of 
  7'65 
  units, 
  or 
  27*5 
  units 
  per 
  kilogram 
  

   of 
  uranium. 
  This 
  gives 
  for 
  \2 
  ^ 
  value 
  5*1 
  x 
  10"^, 
  and 
  for 
  

   a/Xo 
  19,600 
  years. 
  

  

  Experiment 
  III. 
  is 
  very 
  interesting 
  on 
  account 
  of 
  the 
  very 
  

   small 
  total 
  amount 
  of 
  radium 
  present, 
  though 
  the 
  quantity 
  of 
  

   uranium 
  is 
  considerably 
  greater 
  than 
  in 
  the 
  other 
  two. 
  It 
  

   has 
  not 
  been 
  in 
  progress 
  long 
  enough 
  to 
  give 
  the 
  slope 
  of 
  

   the 
  curve 
  very 
  accurately. 
  As 
  drawn 
  in 
  fig. 
  3 
  the 
  growth 
  

   in 
  ^yi 
  years 
  is 
  7*5 
  units, 
  or 
  18*4 
  units 
  per 
  kilogram. 
  The 
  

   calculated 
  value 
  of 
  \^ 
  is 
  3-8x10-% 
  and 
  of 
  l/X^ 
  26,000 
  

   years. 
  

  

  The 
  experiment 
  is 
  of 
  interest 
  in 
  this 
  way. 
  If 
  the 
  growth 
  

   of 
  radium 
  had 
  been 
  proceeding 
  at 
  the 
  same 
  rate 
  as 
  in 
  Experi- 
  

   ment 
  I., 
  in 
  .-^8 
  years 
  10'6 
  units 
  of 
  radium 
  should 
  have 
  been 
  

   produced, 
  whereas 
  the 
  total 
  amount 
  of 
  radium 
  now 
  present 
  

   is 
  less 
  than 
  this, 
  being 
  so 
  far 
  as 
  the 
  measurements 
  indicate 
  

   only 
  8'5 
  units. 
  Even 
  if 
  it 
  is 
  assumed 
  that 
  this 
  difference 
  is 
  

   due 
  to 
  errors 
  of 
  experiment, 
  it 
  is 
  diflScult 
  to 
  believe 
  that 
  the 
  

   solution 
  as 
  initially 
  prepared 
  contained 
  absolutely 
  no 
  radium. 
  

   The 
  results 
  of 
  the 
  three 
  experiments 
  taken 
  together 
  thus 
  

   indicate 
  that 
  the 
  rate 
  of 
  growth 
  of 
  radium 
  in 
  terms 
  of 
  the 
  

   square 
  of 
  the 
  time 
  is 
  less 
  for 
  the 
  first 
  three 
  years 
  than 
  for 
  

   the 
  subsequent 
  year. 
  This 
  points 
  to 
  the 
  existence 
  of 
  one 
  or 
  

   more 
  intermediate 
  bodies 
  of 
  relatively 
  short 
  period 
  in 
  the 
  

   series, 
  which 
  would 
  retard 
  the 
  rate 
  of 
  production 
  of 
  radium 
  

   initially. 
  

  

  The 
  actual 
  measurements 
  of 
  the 
  initial 
  quantity 
  of 
  radium 
  

   in 
  Experiment 
  I. 
  bear 
  this 
  view 
  out, 
  although 
  it 
  muse 
  be 
  

   remembered 
  th;jt 
  the 
  errors 
  of 
  measurement 
  initially 
  were 
  

   very 
  much 
  greater 
  than 
  now, 
  and 
  this 
  evidence 
  thus 
  only 
  

   has 
  a 
  doubtful 
  value. 
  For 
  Experiment 
  II, 
  the 
  initial 
  

   measurements 
  may 
  be 
  rejected, 
  as 
  the 
  quantity 
  of 
  radium 
  

  

  Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  108. 
  Dec. 
  1909. 
  3 
  M 
  

  

  