﻿and 
  Chemical 
  Reactions 
  in 
  Heterogeneous 
  Systems. 
  553 
  

  

  constants 
  icoidd 
  present, 
  in 
  nvj 
  opinion, 
  a 
  striking 
  jjroof 
  that 
  

   the 
  application 
  of 
  the 
  above 
  di 
  fusion 
  concejJtions 
  here 
  is 
  entirely 
  

   out 
  of 
  place. 
  

  

  (f) 
  Not 
  only 
  is 
  there 
  no 
  proof 
  for 
  their 
  values 
  of 
  S, 
  but 
  

   the 
  assumption 
  of 
  the 
  existence 
  of 
  the 
  layer 
  at 
  all 
  is 
  

   extremely 
  unnatural, 
  and 
  is 
  evidently 
  wrong. 
  My 
  equation 
  

   Jwlds 
  good 
  also 
  for 
  evaporation 
  of 
  solids 
  and 
  liquids, 
  loliere 
  tJie 
  

   diffusion 
  of 
  the 
  gas 
  into 
  the 
  lohole 
  gaseous 
  space 
  is 
  instantaneous, 
  

   ami 
  where 
  there 
  is 
  nothing 
  to 
  keep> 
  the 
  gas 
  saturated 
  at 
  the 
  

   surface 
  of 
  the 
  solid, 
  and 
  in 
  the 
  rest 
  of 
  the 
  space 
  unsaturated, 
  

   where 
  there 
  is 
  nothing 
  to 
  prevent 
  the 
  moving 
  molecules 
  from 
  

   reaching 
  the 
  very 
  solid 
  on 
  its 
  way. 
  If 
  this 
  is 
  so 
  for 
  the 
  gaseous 
  

   space, 
  wliere 
  is 
  the 
  need 
  and 
  the 
  force 
  of 
  these 
  most 
  unnatural 
  

   assumptions 
  as 
  regards 
  the 
  solution 
  ? 
  

  

  Sote 
  cdso, 
  that 
  the 
  laics 
  of 
  Boyle 
  and 
  Gay 
  Lussac 
  and 
  

   the 
  whole 
  kinetic 
  theory 
  icere 
  deduced 
  icithout 
  the 
  assumption 
  

   of 
  the 
  existence 
  of 
  such 
  a 
  laijer 
  and 
  ptresuppose 
  that 
  the 
  gas 
  

   can 
  reach 
  the 
  very 
  solid. 
  Sote, 
  that 
  vaiit 
  Hojf's 
  laws 
  of 
  

   Boyle 
  and 
  Gay 
  Lussac 
  in 
  solutions 
  presuppose 
  that 
  the 
  sub- 
  

   stance 
  in 
  solution 
  behaves 
  in 
  a 
  similar 
  manner 
  to 
  the 
  substance 
  

   in 
  the 
  gaseous 
  space. 
  All 
  this 
  is, 
  in 
  my 
  opinion, 
  a 
  solid 
  

   proof 
  aoainst 
  the 
  above 
  fundamental 
  assumptions 
  of 
  the 
  

   diffusion 
  theory. 
  

  

  (d) 
  I 
  now 
  pass 
  to 
  an 
  important 
  experimental 
  test 
  of 
  the 
  

   diffusion 
  theory, 
  and 
  this 
  is 
  the 
  influence 
  of 
  temperature 
  upon 
  

   the 
  speed 
  of 
  reaction. 
  If 
  the 
  velocity 
  of 
  reaction 
  is, 
  as 
  we 
  

   are 
  told, 
  regulated 
  by 
  diffusion, 
  then 
  A 
  must 
  vary 
  with 
  

   temperature 
  as 
  the 
  diffusion 
  constant 
  F 
  does. 
  This, 
  in 
  my 
  

   opinion, 
  would 
  be 
  a 
  serious 
  proof 
  for 
  the 
  diffusion 
  theory 
  

   if 
  it 
  proved 
  to 
  hold 
  good, 
  since 
  it 
  would 
  have 
  represented 
  a 
  

   quantitative 
  test 
  of 
  the 
  theory 
  instead 
  of 
  remaining 
  a 
  mere 
  

   assertion 
  with 
  no 
  proof 
  whatever, 
  Now 
  Nernst 
  and 
  Brunner 
  

   investigated 
  the 
  speed 
  of 
  solution 
  of 
  benzoic 
  acid 
  at 
  different 
  

   temperatures. 
  They 
  find 
  A 
  at 
  20^ 
  = 
  2-30, 
  at 
  30°= 
  I'O 
  x 
  2-30, 
  

   i. 
  e. 
  an 
  increase 
  of 
  5 
  per 
  cent, 
  per 
  degree, 
  while 
  it 
  ought 
  to 
  

   have 
  been 
  only 
  2"5 
  per 
  cent, 
  according 
  to 
  the 
  variation 
  of 
  the 
  

   diffusion 
  constant. 
  One 
  would 
  say, 
  this 
  is 
  a 
  most 
  decisive 
  

   proof 
  against 
  their 
  theory 
  ; 
  but 
  there 
  is 
  always, 
  according 
  to 
  

   Nernst 
  and 
  Brunner, 
  a 
  way 
  out 
  of 
  the 
  difficulty. 
  It 
  is 
  enough 
  

   for 
  this 
  to 
  assume 
  that 
  the 
  adhesion 
  and 
  with 
  it 
  the 
  thickness 
  

   of 
  the 
  layer 
  h, 
  become 
  smaller 
  with 
  temperature. 
  The 
  sole 
  

   effect 
  of 
  the 
  introduction 
  of 
  this 
  layer 
  8 
  is 
  to 
  prove 
  some- 
  

   thing 
  without 
  proof. 
  To 
  this 
  8 
  all 
  sorts 
  of 
  properties 
  are 
  

   now 
  attributed, 
  without, 
  however, 
  the 
  least 
  evidence 
  being 
  

   produced. 
  The 
  diffusion-constant 
  F 
  is 
  a 
  clear, 
  known 
  physical 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  106. 
  Oct. 
  1909. 
  2 
  P 
  

  

  