﻿260 
  

  

  Mr. 
  L. 
  Vegard 
  : 
  Researches 
  upon 
  

  

  This 
  experiment 
  shows 
  the 
  good 
  effect 
  of 
  using 
  a 
  higher 
  

   potential 
  lor 
  a 
  short 
  time. 
  This 
  will 
  have 
  a 
  similar 
  effect 
  as 
  

   the 
  remaking 
  of 
  the 
  membrane 
  under 
  pressure 
  which 
  is 
  used 
  

   by 
  Berkley 
  and 
  Hartley. 
  But 
  at 
  the 
  same 
  time 
  the 
  experi- 
  

   ments 
  show 
  that 
  the 
  resistance 
  of 
  the 
  membrane, 
  when 
  the 
  

   latter 
  is 
  kept 
  unaltered, 
  largely 
  depends 
  upon 
  the 
  potential. 
  

  

  The 
  effect 
  is 
  examined 
  more 
  closely 
  by 
  some 
  measurements 
  

   carried 
  out 
  at 
  the 
  Cavendish 
  Laboratory. 
  The 
  mode 
  of 
  

   proceeding 
  was 
  about 
  the 
  same 
  as 
  in 
  the 
  first 
  experiment. 
  

   The 
  cell 
  A 
  was 
  electrolysed 
  at 
  constant 
  temperature 
  up 
  to 
  

   maximum 
  of 
  resistance. 
  Then 
  the 
  potential 
  was 
  changed 
  

   as 
  suddenly 
  as 
  possible 
  and 
  the 
  resistance 
  measured. 
  The 
  

   measurements 
  were 
  made 
  by 
  a 
  d'Arsonval 
  galvanometer 
  put 
  

   as 
  a 
  shunt 
  to 
  the 
  head 
  circuit, 
  and 
  the 
  resistance 
  was 
  directly 
  

   compared 
  with 
  a 
  standard 
  resistance 
  of 
  100,000 
  ohms 
  put 
  

   into 
  the 
  circuit 
  instead 
  of 
  the 
  cell. 
  With 
  different 
  potentials 
  

   I 
  had 
  to 
  use 
  a 
  different 
  shunt-resistance 
  so 
  as 
  to 
  get 
  a 
  suitable 
  

   deflexion, 
  but 
  the 
  deflexion 
  for 
  the 
  standard 
  resistance 
  was 
  

   found 
  for 
  each 
  potential, 
  the 
  resistance 
  being 
  thus 
  directly 
  

   compared 
  with 
  the 
  standard. 
  

  

  As 
  the 
  electrolysis 
  had 
  to 
  be 
  stopped 
  for 
  some 
  minutes 
  during 
  

   the 
  experiments, 
  some 
  change 
  in 
  the 
  membrane 
  resistance 
  was 
  

   to 
  be 
  feared, 
  and, 
  as 
  a 
  matter 
  of 
  fact, 
  by 
  going 
  back 
  to 
  the 
  

   original 
  potential 
  the 
  resistance 
  had 
  fallen 
  about 
  1*4 
  per 
  cent. 
  ; 
  

   but 
  as 
  the 
  time 
  for 
  each 
  reading 
  was 
  noticed, 
  by 
  assuming 
  

   a 
  constant 
  rate 
  of 
  fall 
  the 
  measurements 
  could 
  be 
  reduced 
  to 
  

   the 
  same 
  point 
  of 
  time. 
  The 
  result 
  is 
  given 
  in 
  the 
  table. 
  

  

  Temperature 
  11°' 
  5. 
  

  

  Potential. 
  

  

  Resistance. 
  

  

  1 
  

   a= 
  R- 
  

  

  41 
  volts. 
  

  

  208 
  XlO 
  3 
  ohms. 
  

  

  4-81x10-6 
  

  

  85 
  „ 
  

  

  200 
  „ 
  

  

  5-00 
  : 
  , 
  

  

  117 
  „ 
  

  

  191 
  „ 
  

  

  524 
  „ 
  

  

  153 
  „ 
  

  

  176 
  „ 
  

  

  5-68 
  „ 
  

  

  199 
  „ 
  

  

  147 
  „ 
  

  

  6-80 
  „ 
  

  

  As 
  we 
  see, 
  the 
  current 
  system 
  does 
  not 
  follow 
  Ohm's 
  law, 
  

   the 
  resistance 
  falls 
  with 
  increasing 
  potential, 
  and 
  the 
  greater 
  

   the 
  potential 
  the 
  more 
  rapid 
  the 
  fall. 
  

  

  The 
  table 
  also 
  contains 
  the 
  quantity 
  a 
  = 
  ^ 
  , 
  which 
  measures 
  

  

  the 
  conductivity 
  of 
  the 
  system. 
  The 
  experiments 
  give 
  « 
  as 
  a 
  

  

  