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  [ 
  846 
  ] 
  

  

  XC. 
  Tlie 
  JRelation 
  between 
  Uranium 
  and 
  Radium. 
  — 
  IV.* 
  

   Bi/ 
  Feederick 
  Soddt, 
  il/.A.t 
  

  

  THE 
  measurements 
  of 
  the 
  amount 
  of 
  radium 
  in 
  the 
  

   uranium 
  solutions 
  purified 
  and 
  prepared 
  by 
  Mr. 
  T. 
  D. 
  

   Mackenzie 
  have 
  now 
  been 
  in 
  progress 
  for 
  nearly 
  four 
  years, 
  

   and 
  during 
  the 
  past 
  year 
  have 
  all 
  begun 
  to 
  yield 
  certain 
  

   evidence 
  of 
  the 
  growth 
  of 
  radium. 
  It 
  may 
  be 
  recalled 
  that 
  

   the 
  quantity 
  of 
  radium 
  in 
  the 
  oldest 
  preparation, 
  which 
  con- 
  

   tained 
  255 
  grams 
  of 
  uranium, 
  remained 
  almost 
  constant 
  

   within 
  the 
  error 
  of 
  measurement 
  for 
  the 
  first 
  two 
  years,, 
  

   while 
  in 
  the 
  next 
  year 
  a 
  very 
  slight 
  increase 
  was 
  noticed.. 
  

   It 
  was 
  deduced 
  from 
  this 
  result 
  that 
  the 
  period 
  of 
  average 
  

   life 
  of 
  the 
  intermediate 
  parent 
  of 
  radium 
  (ionium) 
  must 
  not 
  

   be 
  less 
  than 
  .1 
  6,500 
  years, 
  on 
  the 
  assumption 
  that, 
  neglecting 
  

   uranium 
  X, 
  it 
  was 
  the 
  onli/ 
  intermediate 
  body 
  in 
  the 
  dis- 
  

   integration 
  series. 
  During 
  the 
  fourth 
  year, 
  now 
  nearly 
  

   passed, 
  the 
  measurements 
  have 
  been 
  taken 
  to 
  a 
  higher 
  degree 
  

   of 
  accuracy 
  than 
  formerly, 
  various 
  improvements 
  having 
  

   been 
  effected, 
  and 
  these 
  have 
  established 
  that 
  the 
  production 
  

   of 
  radium 
  within 
  this 
  period 
  has 
  been 
  going 
  on 
  at 
  a 
  rate 
  

   proportional 
  to 
  the 
  square 
  of 
  the 
  time, 
  within 
  the 
  error 
  of 
  

   measurement. 
  As 
  the 
  methods 
  employed 
  are 
  the 
  outcome 
  

   of 
  considerable 
  experience, 
  and 
  as 
  the 
  details 
  are 
  of 
  im- 
  

   portance 
  in 
  securing 
  accuracy, 
  it 
  may 
  be 
  useful 
  to 
  give 
  a 
  

   short 
  account 
  of 
  them 
  as 
  they 
  are 
  now 
  carried 
  out, 
  though 
  

   they 
  do 
  not 
  involve 
  anything 
  new 
  in 
  general 
  principle. 
  

   Throughout 
  the 
  term 
  " 
  unit 
  leak 
  ^' 
  will 
  be 
  used 
  to 
  denote 
  a 
  

   leak 
  of 
  1 
  division 
  a 
  minute 
  in 
  the 
  electroscope, 
  and 
  the 
  term 
  

   "unit 
  of 
  radium^' 
  the 
  quantity 
  10"^^ 
  gram. 
  One 
  division 
  

   of 
  the 
  eyepiece-scale 
  of 
  the 
  microscope 
  equals 
  '023 
  mm. 
  

  

  II. 
  Metliod 
  of 
  Testing 
  for 
  Radium. 
  

  

  The 
  uranium 
  preparations 
  at 
  the 
  commencement 
  of 
  the 
  

   fourth 
  year 
  were 
  removed 
  from 
  the 
  mercury-pump, 
  to 
  which. 
  

  

  * 
  I. 
  PMl. 
  Mag. 
  June 
  190o, 
  p. 
  768 
  ; 
  II. 
  (in 
  conjunction 
  with 
  T. 
  D. 
  

   Mackenzie, 
  B.Sc), 
  ibid. 
  Aug. 
  1907, 
  p. 
  272 
  j 
  III. 
  ibid. 
  Oct. 
  1908, 
  

   p. 
  634. 
  

  

  A 
  preliminary 
  account 
  of 
  some 
  of 
  the 
  results 
  in 
  this 
  paper 
  appeared 
  in 
  

   a 
  letter 
  to 
  'Nature,' 
  May 
  13th, 
  1909, 
  p. 
  308, 
  and 
  the 
  Physikalische 
  

   Zeitschrift, 
  1909, 
  p. 
  396. 
  The 
  paper 
  was 
  read 
  on 
  Oct. 
  22nd, 
  1909, 
  before- 
  

   the 
  Physical 
  Society 
  of 
  London, 
  under 
  the 
  title 
  " 
  The 
  Production 
  of 
  

   Radinm 
  from 
  Uranium." 
  

  

  t 
  Communicated 
  by 
  the 
  Author. 
  

  

  