﻿with 
  tlte 
  Radium 
  Emanation. 
  305 
  

  

  Discussion 
  of 
  Experiments. 
  

  

  Preliminary 
  experiments 
  showed 
  that 
  the 
  volume 
  of 
  the 
  

   emanation 
  was 
  certainly 
  much 
  lower 
  than 
  that 
  found 
  by 
  

   Ramsay 
  and 
  Cameron 
  ; 
  the 
  purity 
  of 
  the 
  emanation 
  was 
  

   examined 
  spectroscopically 
  in 
  the 
  capillary 
  itself 
  without 
  the 
  

   use 
  of 
  electrodes. 
  Some 
  tinfoil 
  was 
  wound 
  round 
  the 
  upper 
  

   and 
  lower 
  part 
  of 
  the 
  capillary 
  and 
  a 
  discharge 
  produced 
  in 
  

   the 
  capillary 
  by 
  means 
  of 
  a 
  small 
  induction-coil. 
  The 
  spec- 
  

   trum 
  was 
  examined 
  by 
  a 
  Hilger 
  spectroscope, 
  by 
  means 
  of 
  

   which 
  the 
  wave-length 
  of 
  the 
  lines 
  could 
  be 
  read 
  off 
  directly. 
  

   In 
  the 
  preliminary 
  experiments, 
  the 
  spectrum 
  observed 
  was 
  the 
  

   ordinary 
  band 
  spectrum 
  ascribed 
  to 
  carbon 
  dioxide 
  with 
  some 
  

   of 
  the 
  mercury 
  lines 
  and 
  occasionally 
  a 
  few 
  other 
  very 
  faint 
  

   lines. 
  Precautions 
  were 
  then 
  taken 
  to 
  get 
  rid 
  of 
  the 
  carbon 
  

   dioxide. 
  Phosphorus 
  pentoxide 
  instead 
  of 
  tap 
  grease 
  was 
  

   used 
  to 
  lubricate 
  the 
  stopcocks. 
  The 
  emanation 
  was 
  always 
  

   left 
  in 
  the 
  presence 
  of 
  solid 
  caustic 
  potash 
  some 
  time 
  before 
  

   its 
  introduction 
  into 
  the 
  U-tube. 
  In 
  addition 
  the 
  emanation 
  

   after 
  the 
  uncondensed 
  gases 
  were 
  pumped 
  off 
  was 
  left 
  in 
  

   contact 
  with 
  the 
  tube 
  D 
  which 
  was 
  coated 
  with 
  a 
  layer 
  of 
  

   caustic 
  potash. 
  Notwithstanding 
  all 
  these 
  precautions 
  it 
  was 
  

   found 
  at 
  first 
  impossible 
  to 
  remove 
  the 
  last 
  traces 
  of 
  carbon 
  

   dioxide. 
  Attempts 
  were 
  made 
  to 
  remove 
  the 
  greater 
  part 
  of 
  

   the 
  residual 
  C0 
  2 
  by 
  fractional 
  distillation, 
  using 
  the 
  pentane 
  

   bath 
  for 
  temperature 
  adjustment, 
  but 
  with 
  only 
  partial 
  success. 
  

   There 
  appears 
  to 
  be 
  some 
  evidence 
  that 
  the 
  emanation 
  

   prefers 
  to 
  condense 
  with 
  the 
  C0 
  2 
  which 
  is 
  present, 
  and 
  is 
  

   released 
  with 
  it 
  when 
  the 
  temperature 
  rises. 
  Finally, 
  after 
  

   a 
  large 
  number 
  of 
  experiments, 
  it 
  was 
  found 
  essential 
  to 
  allow 
  

   the 
  emanation 
  after 
  purification 
  from 
  other 
  gases 
  to 
  remain 
  

   five 
  or 
  six 
  hours, 
  preferably 
  24 
  hours, 
  in 
  the 
  presence 
  of 
  the 
  

   caustic 
  potash 
  tube 
  D. 
  When 
  this 
  was 
  done, 
  it 
  was 
  found 
  

   that 
  the 
  volume 
  of 
  the 
  gas 
  obtained 
  in 
  the 
  capillary 
  was 
  much 
  

   reduced 
  and 
  the 
  carbon-dioxide 
  spectrum 
  became 
  much 
  

   fainter. 
  The 
  reason 
  why 
  such 
  a 
  long 
  time 
  of 
  exposure 
  to 
  

   caustic 
  potash 
  is 
  required 
  is 
  not 
  at 
  all 
  clear. 
  It 
  may 
  be 
  due 
  

   to 
  the 
  very 
  slow 
  absorption 
  of 
  the 
  last 
  traces 
  of 
  carbon 
  dioxide 
  

   by 
  caustic 
  potash. 
  It 
  is 
  possible, 
  however, 
  that 
  the 
  spectrum 
  

   ascribed 
  to 
  C0 
  2 
  is 
  in 
  reality 
  due 
  to 
  carbon 
  monoxide 
  in 
  the 
  

   presence 
  of 
  oxygen. 
  There 
  is 
  considerable 
  difference 
  of 
  

   opinion 
  among 
  spectroscopists 
  on 
  this 
  point. 
  If 
  the 
  disturbing 
  

   gas 
  is 
  CO 
  it 
  must 
  first 
  be 
  converted 
  into 
  C0 
  2 
  in 
  the 
  presence 
  

   of 
  oxygen 
  by 
  the 
  action 
  of 
  the 
  emanation 
  before 
  absorption 
  

   by 
  the 
  caustic 
  potash. 
  This 
  would 
  account 
  for 
  the 
  long 
  time 
  

   required 
  for 
  complete 
  absorption. 
  As 
  far 
  as 
  my 
  experience 
  

  

  