﻿Osmosis 
  and 
  Osmotic 
  Pressure. 
  403 
  

  

  The 
  analysis 
  of 
  solution 
  gave 
  no 
  change 
  in 
  the 
  concentra- 
  

   tion, 
  and 
  the 
  water 
  in 
  the 
  cell 
  gave 
  no 
  rotation. 
  Then 
  we 
  

   get: 
  

  

  ir 
  / 
  = 
  2-88atm 
  . 
  d'^40-0 
  gr./l. 
  

  

  14. 
  The 
  following 
  measurements 
  were 
  carried 
  out 
  at 
  the 
  

   Cavendish 
  Laboratory. 
  The 
  osmometer 
  is 
  as 
  a 
  whole 
  the 
  

   same 
  as 
  before. 
  A 
  new 
  manometer 
  had 
  to 
  be 
  used, 
  and 
  in 
  

   order 
  to 
  increase 
  the 
  accuracy 
  for 
  measuring 
  high 
  pressures 
  

   the 
  end 
  of 
  the 
  manometer 
  had 
  a 
  smaller 
  diameter 
  than 
  the 
  

   rest. 
  In 
  the 
  end 
  of 
  the 
  tube 
  was 
  a 
  little 
  column 
  of 
  mercury, 
  

   so 
  the 
  enclosed 
  air 
  now 
  could 
  be 
  measured 
  between 
  two 
  

   mercury 
  columns 
  in 
  a 
  calibrated 
  tube. 
  The 
  calibration 
  was 
  

   done 
  in 
  the 
  same 
  manner 
  as 
  earlier 
  described. 
  

  

  Further, 
  the 
  glass 
  tubes 
  connecting 
  the 
  osmometer 
  with 
  

   the 
  compressor 
  and 
  the 
  manometer 
  were 
  replaced 
  by 
  two 
  steel 
  

   tubes. 
  The 
  tube 
  to 
  the 
  compressor 
  could 
  be 
  closed 
  by 
  means 
  

   of 
  screw-tap 
  shown 
  in 
  PI. 
  IX. 
  fig. 
  7. 
  This 
  was 
  done 
  to 
  secure 
  

   a 
  safe 
  tightening 
  for 
  very 
  high 
  pressures. 
  The 
  compressor 
  

   being 
  made 
  of 
  brass 
  seemed 
  to 
  a 
  very 
  small 
  extent 
  to 
  yield 
  at 
  

   high 
  pressures, 
  and 
  thus 
  give 
  rise 
  to 
  a 
  small 
  leak 
  between 
  the 
  

   pieces 
  E 
  and 
  D 
  (fig. 
  2, 
  PI. 
  VIII.). 
  When 
  the 
  passage 
  between 
  

   the 
  osmometer 
  and 
  the 
  compressor 
  was 
  open, 
  the 
  passage 
  to 
  

   the 
  screw 
  (a) 
  could 
  be 
  closed 
  by 
  the 
  inner 
  cylinder 
  pressing 
  

   against 
  a 
  leather 
  ring 
  ; 
  thus 
  the 
  movement 
  of 
  the 
  screw 
  was 
  

   restricted 
  to 
  about 
  half 
  a 
  revolution. 
  The 
  conical 
  tap 
  (7) 
  

   that 
  can 
  turn 
  in 
  the 
  cylinder 
  (/3) 
  is 
  made 
  of 
  very 
  hard 
  steel 
  

   pressing 
  against 
  the 
  softer 
  metal 
  of 
  the 
  steel 
  tube. 
  This 
  

   screw-tap, 
  made 
  at 
  the 
  Cavendish 
  Laboratory, 
  has 
  worked 
  

   quite 
  perfectly. 
  

  

  Besides 
  a 
  determination 
  of 
  the 
  equilibrium 
  pressures, 
  

   these 
  experiments 
  have 
  been 
  especially 
  directed 
  to 
  a 
  closer 
  

   investigation 
  of 
  the 
  velocity 
  curve 
  \ 
  ! 
  and 
  at 
  the 
  same 
  time 
  

   some 
  experiments 
  have 
  been 
  made 
  to 
  determine 
  the 
  effect 
  of 
  

   temperature 
  upon 
  the 
  pressure 
  7r 
  '. 
  The 
  cell 
  is 
  the 
  same 
  as 
  

   used 
  in 
  the 
  experiments 
  at 
  Christiania. 
  

  

  Experiment 
  I. 
  

  

  Velocities 
  corresponding 
  to 
  a 
  solution 
  containing 
  520 
  gr. 
  

   in 
  the 
  litre 
  at 
  15° 
  C. 
  The 
  apparatus 
  was 
  put 
  up 
  on 
  the 
  5th 
  

   of 
  March. 
  The 
  observations 
  were 
  made 
  March 
  6 
  and 
  7. 
  

   The 
  temperature 
  in 
  the 
  osmometer 
  was 
  11°' 
  5 
  C. 
  The 
  velocity 
  

   of 
  osmotic 
  flow 
  was 
  examined 
  for 
  different 
  values 
  of 
  7r, 
  

   observing- 
  the 
  change 
  of 
  water-level 
  in 
  a 
  certain 
  time. 
  With 
  

   somewhat 
  large 
  velocities 
  the 
  time 
  for 
  each 
  pressure 
  was 
  

  

  2E 
  2 
  

  

  