﻿270 
  Researches 
  upon 
  Osmosis 
  and 
  Osmotic 
  Pressure. 
  

  

  If 
  this 
  can 
  be 
  considered 
  a 
  general 
  rule 
  it 
  must 
  take 
  place 
  

   when 
  we 
  have 
  only 
  one 
  kind 
  of 
  leak, 
  then 
  we 
  get 
  

  

  Hem 
  ember 
  ing 
  that 
  the 
  velocities 
  are 
  positive 
  when 
  the 
  

   height 
  of 
  water-level 
  is 
  increased, 
  we 
  come 
  to 
  the 
  very 
  

   reasonable 
  conclusion 
  that 
  the 
  osmotic 
  activity 
  is 
  diminished 
  

   by 
  the 
  leak. 
  

  

  From 
  (7) 
  we 
  see 
  that 
  by 
  assuming 
  the 
  whole 
  leak 
  a 
  solution 
  

   leak 
  and 
  finding 
  the 
  pressure 
  7r 
  ', 
  we 
  shall 
  approach 
  the 
  ideal 
  

   pressure, 
  and 
  in 
  the 
  treatment 
  of 
  the 
  observations 
  we 
  shall 
  

   use 
  this 
  correction. 
  

  

  The 
  apparent 
  equilibrium 
  pressure 
  is 
  determined 
  by 
  the 
  

   manometer 
  pressure 
  q, 
  but 
  to 
  this 
  must 
  be 
  added 
  a 
  quantity 
  

   due 
  to 
  the 
  liquids. 
  For 
  the 
  manometer 
  used 
  at 
  Christiania 
  

   we 
  get 
  

  

  7r 
  ' 
  = 
  a-0'44 
  + 
  0'0104a— 
  ^o 
  + 
  Att 
  atm. 
  

  

  a 
  is 
  the 
  manometer 
  reading 
  in 
  cm. 
  For 
  somewhat 
  high 
  

   pressures 
  we 
  can 
  put 
  jp 
  = 
  l. 
  A7r 
  is 
  the 
  correction 
  for 
  the 
  

   leak 
  regarded 
  as 
  a 
  solution 
  leak. 
  To 
  find 
  A7r 
  we 
  shall 
  have 
  

   to 
  find 
  V 
  in 
  the 
  neighbourhood 
  of 
  the 
  apparent 
  equilibrium 
  

   point. 
  Further, 
  we 
  shall 
  have 
  to 
  find 
  the 
  leak 
  corresponding 
  

   to 
  a 
  pressure 
  near 
  to 
  the 
  equilibrium 
  pressure. 
  Then 
  in 
  the 
  

   experiments 
  we 
  ought 
  to 
  keep 
  the 
  pressure 
  on 
  an 
  average 
  

   near 
  to 
  the 
  equilibrium 
  pressure. 
  By 
  analysing 
  the 
  water 
  

   in 
  the 
  cell 
  and 
  by 
  assuming 
  a 
  constant 
  velocity 
  of 
  leak, 
  the 
  

   latter 
  can 
  be 
  found. 
  

  

  On 
  the 
  Determination 
  of 
  the 
  Actual 
  Concentration. 
  

  

  10. 
  The 
  concentration 
  difference 
  between 
  the 
  two 
  sides 
  of 
  

   the 
  membrane 
  in 
  the 
  case 
  of 
  cane-sugar 
  can 
  be 
  altered 
  in 
  

   three 
  different 
  ways 
  : 
  

  

  (1) 
  By 
  the 
  osmotic 
  flow 
  of 
  water 
  into 
  the 
  solution. 
  

  

  (2) 
  By 
  the 
  leaks. 
  

  

  (3) 
  By 
  inversion. 
  

  

  To 
  determine 
  these 
  corrections 
  the 
  following 
  method 
  was 
  

   used 
  : 
  — 
  

  

  A 
  possible 
  inversion 
  was 
  tested 
  with 
  Fehling's 
  solution, 
  and 
  

   in 
  our 
  experiments 
  the 
  first 
  qualitative 
  test 
  gave 
  no 
  mea- 
  

   surable 
  precipitate. 
  The 
  change 
  in 
  concentration 
  on 
  account 
  

   of 
  dilution 
  was 
  found 
  by 
  measuring 
  the 
  angles 
  of 
  polarization 
  

   # 
  and 
  a 
  before 
  and 
  after 
  the 
  osmosis. 
  The 
  concentration 
  (g) 
  

  

  