﻿16 
  

  

  J. 
  Stansfield 
  — 
  Retarded 
  Diffusion 
  and 
  

  

  that 
  part 
  of 
  the 
  gelatine. 
  Liesegang 
  (9) 
  has 
  shown 
  how 
  gradual 
  

   increase 
  of 
  hydrions 
  present 
  in 
  a 
  silver 
  diffusion 
  against 
  chro- 
  

   mate, 
  in 
  gelatine, 
  results 
  in 
  the 
  formation 
  of 
  broader 
  bands, 
  

   i. 
  e. 
  ? 
  not 
  only 
  increases 
  the 
  number 
  of 
  centers 
  of 
  formation 
  of 
  

   the 
  precipitate, 
  but 
  also 
  increases 
  the 
  area 
  over 
  which 
  these 
  

   may 
  form. 
  

  

  In 
  a 
  case 
  where 
  diffusion 
  of 
  silver 
  from 
  a 
  drop 
  and 
  of 
  chro- 
  

   mate 
  from 
  a 
  line 
  drawn 
  around 
  the 
  drop 
  took 
  place 
  through 
  a 
  

   space 
  free 
  from 
  both 
  reagents, 
  the 
  first 
  precipitate 
  did 
  not 
  form 
  

   at 
  the 
  point 
  where 
  the 
  solutions 
  first 
  met. 
  The 
  silver 
  diffusion 
  

  

  Fig. 
  6. 
  

  

  is 
  quite 
  visible 
  as 
  there 
  is 
  a 
  clearly 
  marked 
  line 
  in 
  the 
  gelatine 
  

   at 
  the 
  outward 
  front 
  of 
  the 
  advancing 
  solution. 
  The 
  first 
  

   formed 
  precipitate 
  was 
  situated 
  about 
  one 
  millimeter 
  within 
  

   this 
  line, 
  i. 
  e. 
  nearer 
  the 
  center 
  of 
  the 
  silver 
  drop. 
  This 
  would 
  

   suggest 
  that 
  the 
  halo 
  which 
  surrounds 
  the 
  silver 
  diffusion 
  is 
  an 
  

   area 
  in 
  which 
  the 
  concentration 
  is 
  below 
  the 
  super-saturation 
  

   boundary. 
  

  

  Rate 
  of 
  Diffusion 
  a 
  Controlling 
  JBactor. 
  

  

  From 
  the 
  foregoing 
  it 
  is 
  seen 
  that 
  the 
  explanation 
  offered 
  

   by 
  Ostwald 
  (see 
  page 
  1) 
  has 
  been 
  confirmed 
  by 
  later 
  work. 
  By 
  

   the 
  diffusion 
  outwards 
  of 
  the 
  silver 
  and 
  inwards 
  of 
  the 
  chro- 
  

   mate 
  a 
  depletion 
  of 
  the 
  reservoirs 
  of 
  those 
  ions 
  takes 
  place, 
  

   i. 
  e., 
  the 
  ionic 
  concentration 
  is 
  gradually 
  reduced, 
  with 
  the 
  

   result 
  that 
  the 
  silver 
  ions 
  are 
  enabled 
  to 
  diffuse 
  to 
  a 
  greater 
  

   distance 
  before 
  the 
  precipitation 
  concentration 
  is 
  attained. 
  

  

  