﻿568 
  Dr. 
  Meyer 
  Wilder 
  man 
  on 
  Velocity 
  of 
  Molecular 
  

  

  solidification 
  to 
  a 
  proximity 
  o£ 
  about 
  10~^^ 
  mm., 
  when 
  the 
  

   liquid 
  is 
  not 
  stirred, 
  we 
  have 
  no 
  reason 
  whatever 
  to 
  assume 
  

   that 
  the 
  liquid 
  does 
  not 
  reach 
  the 
  solid 
  to 
  the 
  same 
  proximity 
  

   when 
  we 
  stir 
  the 
  same. 
  For 
  the 
  diffusion 
  conceptions 
  to 
  find 
  

   any 
  application 
  at 
  all 
  it 
  is 
  necessary 
  to 
  prove, 
  not 
  that 
  a 
  satu- 
  

   rated 
  solution 
  can 
  be 
  formed 
  at 
  the 
  surface 
  of 
  the 
  solid 
  (when 
  

   not 
  stirred), 
  but 
  that 
  the 
  solution 
  is 
  inccq-^ahle 
  of 
  entering 
  the 
  

   layer 
  near 
  the 
  solid 
  when 
  it 
  is 
  moved 
  into 
  it 
  by 
  the 
  stirrer, 
  

   diluting 
  the 
  same. 
  The 
  assumption 
  that 
  a 
  saturated 
  solution 
  is 
  

   formed 
  at 
  the 
  solid 
  which 
  passes 
  into 
  the 
  rest 
  of 
  the 
  solution 
  

   by 
  diffusion, 
  overlooks 
  also 
  the 
  fact 
  that 
  the 
  solid 
  in 
  contact 
  

   with 
  its 
  saturated 
  solution 
  ought 
  to 
  he 
  in 
  equilihrium 
  loith 
  it, 
  

   aught 
  not 
  to 
  be 
  able 
  to 
  dissolve 
  any 
  more, 
  and 
  that 
  a 
  reaction 
  of 
  

   solution 
  of 
  the 
  solid 
  cannot 
  possibly 
  oo 
  on, 
  unless 
  the 
  layer 
  

   in 
  the 
  immediate 
  contact 
  with 
  the 
  solid 
  is 
  unsaturated. 
  In 
  

   this 
  notion 
  we 
  are 
  confirmed 
  by 
  the 
  behaviour 
  of 
  a 
  solid 
  in 
  

   contact 
  with 
  its 
  gas, 
  and 
  this 
  forms 
  at 
  present 
  an 
  axiomatic 
  

   notion, 
  which 
  existed 
  for 
  ever 
  so 
  long 
  in 
  physics 
  and 
  che- 
  

   mistry, 
  which 
  led 
  to 
  many 
  useful 
  and 
  fruitful 
  results 
  which 
  

   cannot 
  be 
  given 
  up 
  for 
  the 
  sake 
  of 
  peculiar 
  diffusion 
  con- 
  

   'Ceptions, 
  even 
  if 
  they 
  should 
  seem 
  capable 
  of 
  explaining 
  

   rsome 
  particular 
  case. 
  

  

  Qi) 
  I 
  will 
  next 
  consider 
  the 
  " 
  important 
  argument 
  " 
  of 
  

   ^ernst 
  and 
  Brunner 
  " 
  for 
  the 
  conception 
  of 
  the 
  diffusion 
  

   process." 
  They 
  tell 
  us 
  : 
  — 
  " 
  The 
  true 
  size 
  of 
  the 
  surface 
  is 
  of 
  

   aio 
  importance 
  ; 
  when 
  the 
  originally 
  smooth 
  surface 
  of 
  the 
  

   •solid 
  becomes 
  corroded, 
  the 
  velocity 
  constant 
  A 
  does 
  not 
  

   -change, 
  in 
  spite 
  of 
  the 
  great 
  increase 
  of 
  the 
  surface. 
  Only 
  

   the 
  quadratic 
  dimensions 
  or 
  contour 
  of 
  the 
  surface 
  and 
  not 
  

   ;the 
  microscopic 
  properties 
  of 
  the 
  same 
  are 
  of 
  importance 
  ; 
  

   ■the 
  last 
  should 
  be 
  of 
  im])ortance, 
  if 
  the 
  reaction 
  takes 
  place 
  

   on 
  the 
  surface 
  itself.''^ 
  Assuming, 
  however, 
  that 
  this 
  is 
  true, 
  

   which 
  it 
  is 
  not 
  ■^, 
  it 
  is 
  not 
  to 
  be 
  seen, 
  how 
  this 
  is 
  to 
  be 
  taken 
  as 
  

   a 
  proof 
  for 
  the 
  diffusion 
  conceptions 
  of 
  Nernst 
  and 
  Brunner 
  ? 
  

   If 
  the 
  diffusion 
  layer 
  S 
  were, 
  in 
  comparison 
  with 
  the 
  depth 
  of 
  

   corrosions, 
  very 
  thick, 
  so 
  that 
  the 
  depths 
  of 
  the 
  corrosions 
  

   .could 
  be 
  neglected, 
  such 
  a 
  conclusion 
  would 
  be 
  admissible. 
  

   J3ut 
  when 
  the 
  diff'usion 
  layer 
  8 
  is 
  even 
  according 
  to 
  Nernst 
  

   ;and 
  Brunner 
  only 
  0*02 
  mm. 
  thick, 
  while 
  the 
  corrosions 
  

   .according 
  to 
  them 
  can 
  be 
  as 
  deep 
  as 
  1 
  mm. 
  (without 
  affect- 
  

   ing 
  the 
  constant), 
  it 
  is 
  quite 
  evident 
  that 
  the 
  diffusion 
  layer 
  

   or 
  surface 
  will 
  be 
  as 
  large 
  as 
  the 
  corrosive 
  surface 
  of 
  the 
  

  

  * 
  In 
  my 
  next 
  publication 
  I 
  shall 
  furnish 
  further 
  experimental 
  proof 
  

   ihat 
  reaction 
  does 
  take 
  place 
  at 
  the 
  surface 
  of 
  the 
  solid 
  even 
  in 
  case 
  of 
  

   .substances 
  of 
  no 
  small 
  solubility. 
  

  

  