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  LXI. 
  On 
  Velocity 
  of 
  Molecular 
  and 
  Chemical 
  Reactions 
  in 
  

   Heterogeneous 
  Systems. 
  By 
  Dr. 
  Meyer 
  Wilderman, 
  

   FJuD., 
  B,Sc, 
  (dxon.)*. 
  

  

  Part 
  I. 
  

  

  [Plates 
  XVII. 
  & 
  XVITI.] 
  

  

  I. 
  On 
  Velocity 
  of 
  Molecular 
  Reactions 
  in 
  Heterogeneous 
  Systems 
  

   and 
  the 
  so-called 
  Diffusion 
  Theory, 
  

  

  §1. 
  TN 
  the 
  report 
  of 
  the 
  British 
  Association, 
  1896, 
  Zeit- 
  

   X 
  schriftfUr 
  physikalische 
  C/i^??iie, 
  1899, 
  xxx. 
  pp. 
  348- 
  

   368, 
  and 
  Phil. 
  Mag. 
  July 
  1901, 
  p. 
  50, 
  and 
  some 
  other 
  publi- 
  

   cations, 
  I 
  showed 
  that 
  the 
  velocity 
  of 
  all 
  molecular 
  reactions 
  

   between 
  two 
  parts 
  of 
  the 
  heterogeneous 
  system, 
  such 
  as 
  trans- 
  

   formation 
  of 
  water 
  into 
  ice, 
  ice 
  into 
  water, 
  separation 
  of 
  salt 
  

   from 
  an 
  over 
  saturated 
  solution, 
  solution 
  of 
  salt, 
  evaporation 
  of 
  

   liquids, 
  condensation 
  of 
  vapour, 
  solidification 
  of 
  solutions 
  to 
  

   solids 
  or 
  to 
  solid 
  solutions, 
  &c., 
  all 
  follow 
  the 
  same 
  law 
  ; 
  

  

  £ 
  = 
  C(to-t)(t^tov) 
  = 
  clr(to-t), 
  

  

  L 
  e. 
  the 
  velocity 
  of 
  reaction 
  is 
  at 
  the 
  time 
  t 
  directly 
  propor- 
  

   tional 
  to 
  the 
  remoteness 
  of 
  the 
  system 
  at 
  the 
  time 
  t 
  from 
  the 
  

   point 
  of 
  equilibrium, 
  to 
  — 
  t, 
  and 
  to 
  the 
  surface 
  of 
  contact 
  of 
  

   the 
  reacting 
  parts 
  of 
  the 
  heterogeneous 
  system, 
  t 
  — 
  C, 
  which 
  

   is 
  proportional 
  to 
  2r. 
  Further 
  improvements 
  in 
  the 
  methods 
  

   employed 
  and 
  the 
  photographing 
  of 
  the 
  reactions 
  showed, 
  

   however, 
  the 
  necessity 
  of 
  introduction 
  of 
  the 
  constant 
  K, 
  

   which 
  I 
  called 
  the 
  " 
  instability 
  constant," 
  i. 
  e. 
  

  

  (see 
  the 
  above 
  papers 
  in 
  the 
  Zeitsch. 
  filr 
  physikalische 
  Chemie 
  

   and 
  Phil. 
  Mag.) 
  

  

  = 
  K 
  {to 
  — 
  t) 
  for 
  constant 
  surface. 
  

  

  The 
  above 
  equation 
  was 
  therefore 
  given 
  by 
  me 
  in 
  a 
  most 
  

   general 
  way, 
  including 
  the 
  solution 
  and 
  separation 
  of 
  salts, 
  

   as 
  a 
  particular 
  case 
  only, 
  in 
  a 
  series 
  of 
  publications 
  before 
  

   Noyes 
  and 
  Whitney 
  {Zeitsch. 
  phys. 
  Chem. 
  1897, 
  xxiii. 
  p. 
  689), 
  

   before 
  L. 
  Bruner 
  and 
  Tolloczko 
  {Zeitsch. 
  phys. 
  Chem. 
  1900, 
  

   XXXV. 
  p. 
  283), 
  and 
  long 
  before 
  Nernst 
  and 
  E. 
  Brunner 
  

   {Zeitsch. 
  phys. 
  Chem. 
  1904, 
  xlvii. 
  p. 
  52), 
  who 
  all 
  use 
  it 
  for 
  

   the 
  particular 
  case 
  of 
  solutions 
  of 
  salts 
  only. 
  The 
  equation 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  