﻿Osmosis 
  and 
  Osmotic 
  Pressure. 
  259 
  

  

  that 
  the 
  membrane 
  would 
  show 
  i£ 
  we 
  were 
  able 
  to 
  maintain 
  a 
  

   constant 
  structure 
  should 
  lie 
  between 
  the 
  two 
  values. 
  

  

  In 
  order 
  to 
  explain 
  this 
  large 
  temperature 
  effect 
  it 
  would 
  

   be 
  necessary 
  to 
  know 
  the 
  nature 
  of 
  the 
  conductivity 
  at 
  

   maximum. 
  

  

  As 
  long 
  us 
  the 
  resistance 
  is 
  small 
  and 
  increasing, 
  we 
  can 
  

   be 
  sure 
  that 
  the 
  conductivity 
  is 
  mainly 
  o£ 
  electrolytic 
  

   nature 
  ; 
  but 
  it 
  is 
  also 
  possible 
  that 
  electricity 
  can 
  pass 
  

   through 
  the 
  membrane 
  without 
  being 
  carried 
  by 
  the 
  ions 
  

   o£ 
  the 
  fluids, 
  and 
  when 
  the 
  membrane 
  becomes 
  tighter 
  this 
  

   nonelectrolytic 
  conductivity 
  might 
  even 
  be 
  predominant. 
  

  

  That 
  at 
  maximum 
  resistance 
  a 
  considerable 
  electrolytic 
  con- 
  

   ductivity 
  must 
  take 
  place 
  is 
  evident 
  from 
  the 
  following 
  fact. 
  

  

  As 
  we 
  have 
  seen 
  (fig. 
  6) 
  the 
  resistance 
  after 
  electrolysis 
  

   has 
  been 
  stopped 
  will 
  very 
  rapidly 
  diminish 
  ; 
  but 
  we 
  must 
  

   necessarily 
  assume 
  that 
  this 
  breaking-down 
  process 
  is 
  also 
  

   going 
  on 
  under 
  the 
  electrolysis, 
  only 
  that 
  we 
  now 
  have 
  a 
  

   counteracting 
  process 
  in 
  the 
  new 
  building 
  of 
  the 
  membrane. 
  

   At 
  maximum 
  of 
  resistance 
  there 
  must 
  be 
  an 
  electrolytic 
  con- 
  

   duction 
  just 
  sufficient 
  for 
  balancing 
  the 
  breaking-down 
  

   process. 
  And 
  further, 
  if 
  we 
  would 
  imagine 
  that 
  for 
  a 
  

   moment 
  the 
  conductivity 
  was 
  mainly 
  due 
  to 
  a 
  conduction 
  

   through 
  the 
  membrane 
  substance, 
  the 
  current 
  would 
  call 
  forth 
  

   disturbances 
  in 
  the 
  porous 
  structure 
  of 
  the 
  membrane, 
  and 
  

   the 
  latter 
  would 
  very 
  soon 
  break 
  down 
  and 
  give 
  rise 
  to 
  

   electrolytic 
  conduction. 
  

  

  From 
  this 
  it 
  seems 
  probable 
  that 
  the 
  conductivity 
  even 
  at 
  

   maximum 
  resistance 
  is 
  chiefly 
  of 
  electrolytic 
  nature. 
  The 
  

   electric 
  conductivity 
  would 
  then 
  measure 
  the 
  degree 
  of 
  per- 
  

  

  + 
  - 
  

  

  meability 
  of 
  the 
  membrane 
  for 
  the 
  two 
  ions 
  Ca: 
  and 
  : 
  : 
  Fe(CN) 
  6 
  , 
  

   and 
  the 
  temperature 
  effect 
  would 
  mean 
  that 
  by 
  increasing 
  

   temperature 
  the 
  permeability 
  of 
  the 
  membrane 
  is 
  largely 
  

   increased. 
  

  

  The 
  Dependence 
  of 
  the 
  Resistance 
  upon 
  the 
  Potential. 
  

  

  7. 
  In 
  an 
  experiment 
  carried 
  out 
  for 
  preparing 
  the 
  membrane 
  

   with 
  a 
  higher 
  potential, 
  it 
  was 
  noticed 
  that 
  the 
  latter 
  had 
  a 
  

   great 
  effect 
  upon 
  the 
  resistance 
  of 
  the 
  membrane. 
  In 
  this 
  

   experiment, 
  the 
  cell 
  N 
  was 
  electrolysed 
  first 
  by 
  110 
  volts 
  until 
  

   a 
  maximum 
  of 
  resistance 
  of 
  126,000 
  ohms 
  was 
  reached, 
  then 
  

   the 
  potential 
  was 
  raised 
  to 
  220, 
  and 
  the 
  electrolysis 
  continued 
  

   for 
  about 
  15 
  minutes 
  until 
  the 
  membrane 
  had 
  got 
  a 
  resistance 
  

   of 
  116,000 
  ohms. 
  It 
  might 
  seem 
  as 
  if 
  the 
  high 
  potential 
  had 
  

   diminished 
  the 
  resistance, 
  but 
  bv 
  °;oino- 
  back 
  to 
  the 
  orioinal 
  

   potential 
  the 
  resistance 
  suddenly 
  rose 
  to 
  106,000 
  ohms. 
  

  

  