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  Rate 
  of 
  Recombination 
  of 
  Ions 
  in 
  Gases, 
  

  

  The 
  absolute 
  value 
  of 
  the 
  coefficient 
  a. 
  for 
  these 
  two 
  gases 
  

   was 
  also 
  determined. 
  Carbon 
  dioxide 
  presented 
  a 
  little 
  

   difficulty, 
  as 
  the 
  determinations 
  made 
  on 
  it 
  did 
  not 
  keep 
  

   perfectly 
  constant 
  from 
  day 
  to 
  day. 
  A 
  considerable 
  number 
  

   of 
  determinations 
  were 
  made, 
  however, 
  extending 
  over 
  several 
  

   days 
  and 
  the 
  mean 
  of 
  these 
  values 
  taken. 
  This 
  value 
  of 
  a 
  

   was 
  found 
  to 
  be 
  3492 
  x 
  e, 
  which 
  on 
  substituting 
  the 
  value 
  of 
  

   e 
  becomes 
  2*27 
  x 
  10~~ 
  6 
  . 
  This 
  is 
  practically 
  the 
  same 
  as 
  the 
  

   value 
  of 
  the 
  coefficient 
  obtained 
  for 
  air. 
  

  

  The 
  corresponding 
  determination 
  for 
  hydrogen 
  resulted 
  in 
  

   a 
  value 
  only 
  about 
  87 
  per 
  cent, 
  of 
  the 
  value 
  for 
  air. 
  The 
  

   actual 
  result 
  for 
  hydrogen 
  was 
  2938 
  X 
  e, 
  which 
  becomes 
  

   1*91 
  X 
  10~ 
  6 
  on 
  substituting 
  the 
  value 
  of 
  e. 
  From 
  this 
  it 
  

   appears 
  that, 
  although 
  the 
  coefficient 
  of 
  recombination 
  is 
  a 
  

   constant 
  for 
  any 
  gas, 
  it 
  has 
  not 
  necessarily 
  the 
  same 
  value 
  for 
  

   all 
  gases. 
  

  

  Referring 
  again 
  to 
  Prof. 
  Townsend's 
  paper 
  (Phil. 
  Trans. 
  

   Roy. 
  Soc. 
  vol. 
  cxciii. 
  1899) 
  we 
  find 
  that 
  these 
  results 
  are 
  again 
  

   in 
  close 
  agreement 
  with 
  his. 
  The 
  result 
  for 
  hydrogen 
  given 
  

   above 
  is 
  also 
  the 
  mean 
  result 
  of 
  several 
  determinations. 
  

  

  Removal 
  of 
  Nuclei. 
  

  

  Throughout 
  this 
  investigation, 
  care 
  was 
  taken 
  to 
  thoroughly 
  

   dry 
  the 
  gas 
  and 
  to 
  remove 
  dust 
  particles 
  from 
  it 
  before 
  

   allowing 
  it 
  to 
  pass 
  into 
  the 
  cylinder 
  in 
  which 
  the 
  measure- 
  

   ments 
  were 
  made 
  on 
  it. 
  For 
  this 
  purpose, 
  the 
  air 
  which 
  was 
  

   used 
  in 
  the 
  cylinder 
  was 
  first 
  passed 
  slowly 
  through 
  an 
  iron 
  

   tube 
  (about 
  two 
  feet 
  in 
  length) 
  filled 
  with 
  calcium 
  chloride, 
  

   to 
  remove 
  the 
  moisture, 
  and 
  then 
  through 
  a 
  bulb 
  containing 
  

   cotton-wool, 
  to 
  remove 
  any 
  dust 
  particles. 
  

  

  When 
  hydrogen 
  and 
  carbon 
  dioxide 
  were 
  used, 
  the 
  gas 
  was 
  

   passed 
  through 
  a 
  series 
  of 
  drying-bottles 
  containing 
  small 
  

   pieces 
  o£ 
  pumice-stone 
  moistened 
  with 
  strong 
  sulphuric 
  acid, 
  

   and 
  thence 
  through 
  the 
  cotton-wool 
  as 
  before. 
  These 
  pre- 
  

   cautions 
  were 
  taken 
  of 
  course 
  on 
  account 
  of 
  the 
  fact, 
  which 
  

   has 
  been 
  previously 
  investigated 
  (E. 
  Rutherford, 
  Phil. 
  Mag. 
  

   Nov. 
  1897), 
  that 
  when 
  any 
  nuclei 
  are 
  present 
  in 
  the 
  gas, 
  the 
  

   ions 
  collect 
  about 
  these 
  nuclei 
  and 
  become 
  neutralized. 
  The 
  

   number 
  of 
  ions 
  decreases 
  therefore 
  much 
  more 
  rapidly 
  when 
  

   any 
  nuclei 
  are 
  present 
  in 
  the 
  gas 
  than 
  it 
  does 
  if 
  the 
  gas 
  is 
  

   quite 
  free 
  from 
  these 
  particles. 
  As 
  the 
  object 
  was 
  to 
  determine 
  

   the 
  rate 
  of 
  decrease 
  in 
  the 
  number 
  of 
  ions 
  due 
  simply 
  to 
  the 
  

   recombination 
  with 
  one 
  another, 
  the 
  precaution 
  was 
  therefore 
  

   taken 
  to 
  remove 
  all 
  foreign 
  particles 
  from 
  the 
  gas 
  as 
  far 
  as 
  

   possible. 
  

  

  