﻿with 
  the 
  Radium 
  Emanation. 
  309 
  

  

  the 
  emanation 
  had 
  remained 
  nearly 
  11 
  days 
  in 
  the 
  capillary, 
  

   the 
  spectrum 
  of 
  the 
  gas 
  was 
  examined 
  in 
  the 
  capillary 
  as 
  de- 
  

   scribed 
  above. 
  A 
  brilliant 
  spectrum 
  was 
  obtained 
  showing 
  all 
  

   the 
  lines 
  of 
  helium. 
  The 
  spectrum 
  o£ 
  C0 
  2 
  was 
  also 
  observed, 
  

   although 
  weak 
  in 
  intensity 
  compared 
  with 
  that 
  of 
  helium. 
  

   In 
  addition 
  to 
  the 
  mercury 
  lines, 
  a 
  few 
  unidentified 
  bright 
  

   lines 
  were 
  noted. 
  This 
  result 
  is 
  a 
  confirmation 
  of 
  the 
  well- 
  

   known 
  experiment 
  of 
  Ramsay 
  and 
  Soddy, 
  who 
  found 
  that 
  

   the 
  spectrum 
  of 
  helium 
  appeared 
  after 
  some 
  time 
  in 
  a 
  tube 
  

   containing 
  radium 
  emanation. 
  The 
  cause 
  of 
  the 
  increase 
  of 
  

   volume 
  after 
  the 
  minimum 
  is 
  now 
  clear. 
  Assuming 
  that 
  

   the 
  a 
  particles 
  are 
  atoms 
  of 
  helium, 
  the 
  helium 
  would 
  at 
  

   first 
  be 
  fired 
  into 
  the 
  glass. 
  After 
  a 
  time 
  part 
  of 
  it 
  gradually 
  

   escaped 
  and 
  added 
  its 
  volume 
  to 
  the 
  emanation 
  and 
  other 
  

   gases 
  present. 
  It 
  is 
  difficult 
  to 
  be 
  certain 
  how 
  much 
  of 
  the 
  

   helium 
  was 
  retained 
  in 
  the 
  glass 
  of 
  the 
  capillary. 
  If 
  we 
  

   take 
  the 
  initial 
  volume 
  of 
  the 
  emanation 
  to 
  be 
  about 
  that 
  

   observed 
  at 
  the 
  minimum 
  volume, 
  viz. 
  "059 
  c.mm., 
  the 
  volume 
  

   of 
  helium 
  to 
  be 
  expected 
  is 
  about 
  three 
  times 
  this 
  amount. 
  

   This 
  is 
  on 
  the 
  assumption 
  that 
  each 
  a 
  particle 
  expelled 
  is 
  a 
  

   helium 
  atom. 
  The 
  final 
  volume 
  observed 
  after 
  11 
  days 
  was 
  

   *125 
  c.mm., 
  and 
  was 
  probably 
  mainly 
  due 
  to 
  the 
  helium. 
  

  

  Experiment 
  III. 
  — 
  In 
  this 
  case 
  the 
  emanation 
  was 
  very 
  

   carefully 
  purified, 
  after 
  standing 
  for 
  18 
  hours 
  over 
  caustic 
  

   potash. 
  The 
  amount 
  of 
  emanation 
  present 
  corresponded 
  to 
  

   130 
  mos. 
  radium. 
  The 
  initial 
  volume 
  of 
  the 
  emanation 
  was 
  

   *097 
  c.mm. 
  This 
  corresponds 
  to 
  a 
  volume 
  of 
  0'80 
  c.mm. 
  per 
  

   gram 
  of 
  radium. 
  No 
  certain 
  change 
  in 
  volume 
  was 
  observed 
  

   over 
  an 
  interval 
  of 
  15 
  minutes. 
  The 
  emanation 
  was 
  then 
  

   recondensed 
  in 
  the 
  U-tube, 
  which 
  was 
  pumped 
  out 
  again 
  

   using 
  a 
  pentane 
  bath. 
  On 
  introducing 
  the 
  emanation 
  into 
  

   the 
  capillary 
  again, 
  very 
  nearly 
  the 
  same 
  initial 
  volume 
  as 
  

   before 
  was 
  observed. 
  In 
  order 
  to 
  test 
  the 
  purity 
  of 
  the 
  

   emanation, 
  the 
  spectrum 
  of 
  the 
  gas 
  in 
  the 
  capillary 
  was 
  

   examined. 
  A 
  new 
  spectrum 
  of 
  bright 
  lines, 
  certainly 
  due 
  to 
  

   the 
  emanation 
  itself, 
  was 
  observed. 
  Some 
  of 
  the 
  bands 
  of 
  

   the 
  carbon 
  dioxide 
  spectrum 
  were 
  observable. 
  Observations 
  

   were 
  at 
  once 
  begun 
  to 
  determine 
  the 
  wave-lengths 
  of 
  the 
  

   new 
  lines 
  with 
  accuracy. 
  Before 
  this 
  was 
  completed, 
  most 
  

   of 
  the 
  lines 
  due 
  to 
  the 
  emanation 
  suddenly 
  ran 
  out, 
  and 
  the 
  

   carbon 
  dioxide 
  spectrum 
  became 
  more 
  prominent. 
  The 
  

   volume 
  of 
  the 
  gas 
  in 
  the 
  capillary 
  was 
  also 
  found 
  to 
  have 
  

   considerably 
  decreased. 
  It 
  was 
  then 
  observed 
  by 
  the 
  phos- 
  

   phorescence 
  that 
  the 
  emanation 
  was 
  adhering 
  to 
  the 
  walls 
  of 
  

   the 
  capillary, 
  and 
  only 
  a 
  part 
  of 
  the 
  emanation 
  was 
  free 
  in 
  

  

  