﻿Osmosis 
  and 
  Osmotic 
  Pressure. 
  251 
  

  

  was 
  filled 
  with 
  well-cleaned 
  mercury, 
  taking 
  care 
  in 
  doing 
  

   this 
  that 
  no 
  air 
  from 
  without 
  followed 
  the 
  mercury. 
  Then 
  

   the 
  manometer 
  was 
  left 
  to 
  itself 
  till 
  the 
  following 
  day, 
  

   and 
  the 
  temperature 
  in 
  the 
  room, 
  which 
  was 
  found 
  to 
  keep 
  

   fairly 
  constant, 
  examined. 
  

  

  Just 
  before 
  closing 
  the 
  manometer 
  the 
  following 
  observa- 
  

   tions 
  were 
  made 
  : 
  — 
  

  

  1. 
  The 
  pressure 
  of 
  the 
  air 
  observed 
  by 
  means 
  of 
  a 
  mercury 
  

  

  barometer 
  by 
  which 
  the 
  pressure 
  could 
  be 
  read 
  with 
  

   an 
  accuracy 
  of 
  1/25 
  mm. 
  ; 
  the 
  barometer 
  was 
  com- 
  

   pared 
  with 
  the 
  standard 
  barometer 
  at 
  the 
  Meteoro- 
  

   logical 
  Institute, 
  Christiania. 
  

  

  2. 
  Reading 
  of 
  the 
  temperature 
  of 
  the 
  room. 
  

  

  3. 
  Reading 
  of 
  the 
  mercury 
  level 
  in 
  the 
  manometer. 
  

   I. 
  Reading 
  of 
  the 
  position 
  of 
  the 
  open 
  end. 
  

  

  The 
  end 
  was 
  closed 
  very 
  quickly 
  by 
  putting 
  a 
  drop 
  of 
  

   melted 
  glass 
  into 
  the 
  opening 
  and 
  at 
  the 
  same 
  time 
  using 
  

   the 
  flame. 
  It 
  took 
  no 
  more 
  than 
  10 
  seconds 
  from 
  the 
  time 
  

   the 
  gas-flame 
  was 
  lighted 
  till 
  the 
  end 
  was 
  quite 
  closed. 
  

   Furthermore, 
  the 
  manometer 
  was 
  protected 
  from 
  change 
  in 
  

   temperature 
  by 
  means 
  of 
  an 
  asbestos 
  plate 
  put 
  on 
  the 
  end 
  of 
  

   the 
  manometer. 
  

  

  The 
  manometer 
  then 
  was 
  sealed 
  to 
  the 
  capillary 
  from 
  the 
  

   osmometer, 
  and 
  the 
  latter 
  filled 
  with 
  water. 
  This 
  was 
  done 
  

   I>y 
  drawing 
  back 
  the 
  mercury 
  with 
  a 
  water-pump 
  and 
  letting 
  

   the 
  water 
  flow 
  back 
  into 
  the 
  tube. 
  This 
  was 
  done 
  to 
  reduce 
  

   the 
  volume 
  to 
  be 
  filled 
  by 
  the 
  osmotic 
  flow. 
  

  

  The 
  constants 
  of 
  the 
  manometer 
  are 
  the 
  following 
  : 
  — 
  

  

  The 
  air-pressure 
  on 
  closing... 
  B 
  = 
  754*6* 
  mm. 
  Hg 
  at 
  0°; 
  

   „ 
  abs. 
  temperature 
  „ 
  ... 
  T 
  = 
  287*5; 
  

   „ 
  volume 
  of 
  air 
  „ 
  ... 
  v 
  = 
  22*762 
  vol. 
  units. 
  

  

  For 
  the 
  pressure 
  q 
  in 
  the 
  manometer 
  at 
  a 
  temperature 
  T 
  

   and 
  a 
  volume 
  v 
  we 
  have 
  

  

  fc 
  is 
  a 
  correction 
  introduced 
  because 
  the 
  air 
  does 
  not 
  

   exactly 
  follow 
  Boyle's 
  law. 
  I 
  have 
  put 
  

  

  1 
  + 
  *=-^-, 
  

  

  Wo 
  

  

  where 
  p 
  is 
  one 
  atmosphere 
  and 
  all 
  pressures 
  are 
  made 
  at 
  

   0°, 
  and 
  this 
  value 
  I 
  have 
  taken 
  from 
  the 
  measurements 
  made 
  

   by 
  Regnault 
  and 
  Amagat. 
  

  

  