﻿592 
  Mr. 
  J. 
  Satterly 
  on 
  the 
  Amount 
  of 
  

  

  initial 
  leaks 
  and 
  also 
  leaks 
  three 
  hours 
  afterwards 
  ; 
  but 
  usually 
  

   time 
  could 
  not 
  be 
  spared, 
  and 
  after 
  taking 
  the 
  initial 
  leak 
  the 
  

   air 
  was 
  pumped 
  out 
  before 
  the 
  emanation 
  had 
  time 
  to 
  deposit 
  

   any 
  active 
  matter*. 
  Usually 
  the 
  air 
  leak 
  was 
  repeated 
  again 
  

   to 
  test 
  this 
  point. 
  The 
  first 
  aspirator-full 
  was 
  then 
  passed 
  

   into 
  the 
  vessel 
  and 
  the 
  leak 
  again 
  read. 
  From 
  the 
  two 
  sets 
  

   of 
  readings 
  the 
  total 
  leak 
  due 
  to 
  the 
  emanation 
  given 
  off 
  by 
  

   the 
  charcoal 
  tubes 
  could 
  be 
  calculated 
  by 
  deducting 
  the 
  air 
  

   leaks 
  t- 
  Now 
  this 
  emanation 
  is 
  not 
  all 
  due 
  to 
  the 
  air. 
  I 
  found 
  

   that 
  when 
  a 
  charcoal 
  tube 
  is 
  left 
  to 
  itself 
  it 
  gradually 
  accu- 
  

   mulates 
  radium. 
  The 
  amount 
  accumulated 
  in 
  different 
  times 
  

   I 
  measured 
  at 
  odd 
  intervals 
  by 
  heating, 
  collecting, 
  and 
  testing 
  

   as 
  above. 
  From 
  the 
  mean 
  of 
  these 
  auxiliary 
  measurements 
  I 
  

   calculated 
  for 
  each 
  experiment 
  the 
  amount 
  of 
  emanation 
  

   accumulated 
  by 
  the 
  charcoal 
  itself 
  between 
  the 
  last 
  heating 
  

   and 
  the 
  present 
  one. 
  By 
  subtraction 
  the 
  leak 
  due 
  to 
  the 
  ema- 
  

   nation 
  in 
  the 
  air 
  passed 
  through 
  the 
  tubes 
  during 
  the 
  run 
  was 
  

   found. 
  

  

  If 
  the 
  emanation 
  absorbed 
  during 
  an 
  experiment 
  was 
  not 
  

   measured 
  till 
  a 
  day 
  or 
  two 
  after 
  absorption, 
  the 
  amount 
  of 
  

   the 
  emanation 
  when 
  first 
  absorbed 
  was 
  calculated 
  from 
  the 
  

   decay 
  curve 
  of 
  radium 
  emanation 
  (fig. 
  2). 
  

  

  (/>) 
  Measurement 
  of 
  the 
  Emanation 
  from 
  the 
  Solution. 
  — 
  

   The 
  solution 
  given 
  me 
  by 
  Prof. 
  Rutherford 
  was 
  placed 
  in 
  a 
  

   bottle 
  furnished 
  with 
  a 
  stopper 
  and 
  delivery-tubes. 
  Air 
  was 
  

   bubbled 
  i. 
  through 
  the 
  solution, 
  thus 
  removing 
  the 
  emanation. 
  

   If 
  the 
  solution 
  had 
  been 
  allowed 
  to 
  stand 
  for 
  some 
  time 
  

   the 
  emanation 
  would 
  have 
  been 
  accumulated 
  in 
  the 
  solution 
  

   and 
  the 
  first 
  volume 
  of 
  air 
  drawn 
  through 
  would 
  be 
  very 
  

   strongly 
  radioactive. 
  It 
  is 
  essential, 
  therefore, 
  to 
  pass 
  air 
  

   through 
  the 
  solution 
  for 
  some 
  time 
  before 
  beginning 
  the 
  

  

  * 
  Soddy 
  and 
  Mackenzie 
  (Phil. 
  Mag. 
  Aug. 
  1907) 
  recommend 
  that 
  the 
  

   leak 
  be 
  taken 
  8 
  minutes 
  after 
  filling 
  the 
  vessel 
  with 
  emanation. 
  A 
  tem- 
  

   porary 
  maximum 
  occurs 
  about 
  that 
  time, 
  and 
  the 
  leak 
  is 
  comparatively 
  

   constant 
  for 
  about 
  15 
  minutes. 
  This 
  was 
  what 
  I 
  usually 
  did, 
  for 
  my 
  

   readings, 
  though 
  often 
  commenced 
  directly 
  after 
  filling 
  the 
  vessel 
  — 
  

   which 
  itself 
  took 
  some 
  time 
  — 
  lasted 
  about 
  20 
  minutes. 
  

  

  t 
  There 
  will 
  be 
  a 
  quantity 
  of 
  carbon 
  dioxide 
  in 
  the 
  gas 
  collected 
  in 
  the 
  

   aspirators. 
  This, 
  however, 
  had 
  no 
  effect 
  on 
  the 
  air 
  leak. 
  The 
  point 
  

   was 
  tested 
  many 
  times. 
  

  

  % 
  Several 
  experimenters 
  have 
  urged 
  the 
  boiling 
  of 
  the 
  solution 
  to 
  get 
  

   rid 
  of 
  all 
  the 
  emanation, 
  but 
  it 
  seems 
  to 
  me 
  that 
  bubbling 
  through 
  the 
  

   cold 
  solution 
  will 
  put 
  the 
  solution 
  in 
  a 
  steady 
  state 
  which 
  is 
  all 
  that 
  is 
  

   required 
  during 
  the 
  experiment. 
  I 
  tried 
  boiling 
  once, 
  but 
  a 
  long 
  con- 
  

   denser 
  would 
  be 
  required 
  to 
  remove 
  the 
  excessive 
  amount 
  of 
  water-vapour 
  

   carried 
  on 
  by 
  the 
  air-current; 
  and 
  as 
  bubbling 
  seemed 
  to 
  me 
  quite 
  suffi- 
  

   cient, 
  I 
  contented 
  myself 
  with 
  it. 
  

  

  