﻿Forces 
  produced 
  hy 
  Flowing 
  Solutions. 
  589 
  

  

  by 
  Ostwald 
  a 
  method 
  for 
  determining 
  the 
  dissociation 
  of 
  the 
  

   water 
  *. 
  

  

  The 
  fact 
  that 
  glass 
  acts 
  as 
  a 
  hydrogen 
  electrode 
  enables 
  ns 
  

   to 
  state 
  that 
  at 
  ordinary 
  temperatures 
  an 
  increase 
  of 
  a 
  tenth 
  

   power 
  in 
  the 
  concentration 
  of 
  the 
  hydrogen 
  ions 
  produces 
  a 
  

   change 
  in 
  the 
  electromotive 
  force 
  of 
  0*058 
  volt. 
  A 
  solution 
  

   normal 
  as 
  regards 
  hydrogen 
  ions 
  and 
  one 
  normal 
  as 
  regards 
  

   hydroxy 
  1 
  ions 
  show, 
  as 
  is 
  well 
  known, 
  a 
  ratio 
  of 
  10 
  ~^* 
  

   between 
  their 
  hydrogen-ion 
  concentrations. 
  Consequently, 
  

   the 
  change 
  in 
  the 
  electromotive 
  force 
  between 
  glass 
  and 
  

   surrounding 
  liquid, 
  when 
  the 
  latter 
  undergoes 
  this 
  change 
  

   from 
  normal 
  hydrogen 
  to 
  normal 
  hydroxyl 
  ions, 
  wiJl 
  be 
  

   14x 
  0-058 
  = 
  0*812 
  volt 
  ; 
  where 
  both 
  solutions 
  are 
  one-hun- 
  

   dredth 
  normal, 
  this 
  value 
  becomes 
  10 
  x 
  0*058 
  = 
  0*580, 
  and 
  

   with 
  one-thousandth 
  normal 
  solutions, 
  8 
  X 
  0*058 
  = 
  0*464: 
  volt, 
  

   and 
  so 
  on. 
  

  

  The 
  sign 
  of 
  the 
  change 
  is 
  always 
  such 
  that 
  pure 
  water, 
  

   nrbitrarily 
  taken 
  as 
  neutral 
  against 
  glass, 
  in 
  which 
  the 
  con- 
  

   centration 
  of 
  both 
  hydrogen 
  and 
  hydroxyl 
  ions 
  is 
  10"'^, 
  

   becomes 
  positive 
  by 
  increase 
  of 
  hydroxyl 
  ions, 
  negative 
  by 
  

   increase 
  of 
  hydrogen 
  ions. 
  

  

  In 
  light 
  of 
  these 
  facts 
  the 
  potential 
  difference 
  (pi 
  — 
  ^a-, 
  or 
  

  

  its 
  expanded 
  form 
  /^ 
  (LamVs 
  ((^j— 
  c^J 
  -,), 
  does 
  not 
  seem 
  

  

  quite 
  so 
  inaccessible 
  as 
  before. 
  It 
  is 
  now 
  to 
  be 
  expected 
  

   that 
  if 
  the 
  Helmholtz 
  theory 
  is 
  tested 
  with 
  acid 
  and 
  alkaline 
  

   solutions, 
  different 
  values 
  of 
  (pi—(j)a 
  will 
  result, 
  and 
  we 
  may 
  

  

  predict 
  that 
  if 
  the 
  term 
  ^-^ 
  is 
  zero 
  or 
  constant 
  (or 
  Lamb's 
  -> 
  

  

  is 
  constant), 
  the 
  difference 
  between 
  the 
  values 
  will 
  be 
  equal 
  

   to 
  the 
  electromotive 
  force 
  derived 
  from 
  the 
  acidity 
  and 
  

   alkalinity 
  of 
  the 
  applied 
  solutions. 
  

  

  The 
  irregularity 
  of 
  the 
  values 
  for 
  4>i 
  — 
  (t>a 
  found 
  by 
  different 
  

   experimenters 
  leads 
  us 
  to 
  expect 
  that 
  the 
  experimental 
  veri- 
  

   fication 
  is 
  beset 
  with 
  some 
  difficulties, 
  so 
  that 
  perhaps 
  no 
  

   more 
  than 
  a 
  qualitative 
  agreement 
  can 
  be 
  expected. 
  More- 
  

   over, 
  there 
  exists 
  a 
  group 
  of 
  facts 
  which 
  will 
  be 
  discussed 
  at 
  

   the 
  end 
  of 
  the 
  paper, 
  which 
  make 
  it 
  doubtful 
  whether 
  or 
  not 
  

   the 
  interference 
  of 
  another 
  effect 
  will 
  not 
  prevent 
  more 
  than 
  

   qualitative 
  agreement. 
  In 
  view, 
  however, 
  of 
  the 
  fact 
  that 
  

   the 
  values 
  of 
  the 
  single 
  potentials 
  existing 
  at 
  a 
  phase 
  boundary 
  

  

  * 
  ZeiUchr. 
  f. 
  phys. 
  Chemie, 
  xi. 
  p. 
  521 
  (1893) 
  ; 
  cp. 
  the 
  correction 
  by 
  

   Xemst, 
  ihid. 
  xiv. 
  p. 
  loo 
  (1894), 
  and 
  the 
  recent 
  papers 
  bv 
  Lorenz 
  and 
  his 
  

   collaborators, 
  ibid. 
  Ix. 
  p. 
  422 
  (1907) 
  ; 
  Ixvi. 
  p. 
  733 
  (1909). 
  

  

  