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  149 
  ] 
  . 
  

  

  XV. 
  Vapour-Pressures 
  of 
  Carbon 
  Dioxide 
  and 
  of 
  Ethane 
  

   at 
  1 
  emperatures 
  below 
  0° 
  C. 
  By 
  Professor 
  J. 
  P. 
  Kuenen 
  

   and 
  Mr. 
  W. 
  G. 
  Robson 
  *. 
  

  

  ALTHOUGH 
  from 
  Amagat's 
  researches 
  the 
  critical 
  con- 
  

   stants 
  and 
  vapour-pressures 
  above 
  0° 
  C. 
  of 
  carbon 
  

   dioxide 
  are 
  accurately 
  known, 
  much 
  uncertainty 
  exists 
  as 
  to 
  

   the 
  pressures 
  at 
  temperatures 
  below 
  0° 
  C. 
  The 
  results 
  

   obtained 
  by 
  Faraday, 
  Regnault, 
  Cailletet, 
  and 
  others, 
  are 
  

   not 
  consistent 
  ; 
  and 
  as 
  we 
  wanted 
  accurate 
  values 
  of 
  the 
  

   vapour-pressures 
  of 
  this 
  substance 
  — 
  and 
  also 
  the 
  vapour- 
  

   pressures 
  of 
  ethane 
  — 
  in 
  connexion 
  with 
  an 
  investigation 
  on 
  

   mixtures, 
  we 
  resolved 
  to 
  undertake 
  the 
  determinations 
  our- 
  

   selves. 
  

  

  1. 
  The 
  Temperatures. 
  — 
  We 
  obtained 
  the 
  low 
  temperatures 
  

   by 
  using 
  liquids 
  boiling 
  under 
  reduced 
  pressure, 
  the 
  most 
  

   suitable 
  liquids 
  for 
  our 
  purpose 
  being 
  sulphur 
  dioxide 
  | 
  and 
  

   ammonia 
  J. 
  The 
  liquid 
  was 
  collected 
  in 
  a 
  Dewar 
  vacuum- 
  

   vessel 
  of 
  suitable 
  shape, 
  made 
  by 
  Messrs. 
  Bender 
  & 
  Holbein, 
  

   to 
  our 
  specification. 
  Even 
  at 
  the 
  lowest 
  temperatures 
  the 
  

   liquid 
  in 
  this 
  vessel 
  boiled 
  away 
  quite 
  slowly, 
  so 
  that 
  as 
  

   a 
  rule 
  there 
  was 
  plenty 
  of 
  time 
  for 
  taking 
  the 
  readings 
  before 
  

   fresh 
  liquid 
  had 
  to 
  be 
  let 
  into 
  the 
  vessel. 
  

  

  The 
  vacuum 
  vessel 
  was 
  closed 
  at 
  the 
  top 
  by 
  a 
  rubber 
  

   stopper. 
  Through 
  the 
  stopper 
  passed 
  a 
  tube 
  for 
  admitting 
  the 
  

   liquid 
  sulphur 
  dioxide 
  or 
  ammonia, 
  a 
  tube 
  connecting 
  the 
  

   vessel 
  to 
  a 
  water-pump 
  and 
  open 
  mercury-gauge, 
  the 
  ther- 
  

   mometer, 
  and 
  the 
  pressure-tube 
  which 
  contained 
  the 
  carbon 
  

   dioxide 
  or 
  ethane. 
  

  

  In 
  order 
  to 
  keep 
  the 
  pressure 
  under 
  which 
  the 
  liquid 
  

   boiled, 
  as 
  read 
  on 
  the 
  mercury-gauge, 
  constant, 
  it 
  was 
  found 
  

   sufficient 
  to 
  connect 
  the 
  vessel 
  with 
  a 
  large 
  bottle 
  which 
  acted 
  

   as 
  an 
  air-chamber, 
  and 
  to 
  regulate 
  the 
  pressure 
  by 
  means 
  of 
  

   a 
  tap 
  and 
  of 
  two 
  pinching-screws 
  on 
  the 
  rubber 
  connecting 
  

   the 
  pump 
  with 
  the 
  bottle 
  and 
  vessel. 
  Some 
  gas 
  was 
  allowed 
  

   to 
  bubble 
  through 
  the 
  liquid 
  in 
  order 
  to 
  keep 
  it 
  well 
  stirred. 
  

   The 
  only 
  source 
  of 
  inconstancy 
  in 
  the 
  temperature 
  was 
  

   the 
  want 
  of 
  purity 
  of 
  the 
  boiling 
  liquids, 
  especially 
  the 
  

   sulphur 
  dioxide. 
  We 
  had 
  to 
  take 
  the 
  precaution 
  to 
  read 
  

   temperature 
  and 
  pressure 
  as 
  nearly 
  as 
  possible 
  at 
  the 
  same 
  

   moment. 
  Even 
  of 
  the 
  ammonia, 
  although 
  not 
  submitted 
  to 
  

   a 
  preliminary 
  cooling, 
  only 
  moderate 
  quantities 
  were 
  required 
  

  

  * 
  Communicated 
  by 
  the 
  Authors. 
  

  

  t 
  Obtained 
  from 
  Boake, 
  Roberts 
  & 
  Co., 
  Stratford, 
  E. 
  

  

  \ 
  Obtained 
  from 
  the 
  Scotch 
  and 
  Irish 
  Oxygen 
  Co., 
  Glasgow. 
  

  

  