﻿Rhythmic 
  Precijpita 
  tio?i. 
  

  

  11 
  

  

  place 
  of 
  those 
  precipitated. 
  The 
  result 
  is 
  somewhat 
  analogous 
  

   to 
  the 
  thinning 
  of 
  a 
  sheet 
  of 
  rubber 
  by 
  stretching. 
  With 
  the 
  

   diffusion 
  of 
  the 
  chromat-ions 
  farther 
  outward, 
  however, 
  a 
  suffi- 
  

   cient 
  concentration 
  of 
  silver 
  ions 
  to 
  allow 
  of 
  the 
  formation 
  of 
  

   bands 
  will 
  again 
  be 
  met 
  with 
  and 
  the 
  a 
  secondary 
  " 
  bands 
  will 
  

   result. 
  

  

  A 
  similar 
  explanation 
  would 
  apply 
  to 
  the 
  unhanded 
  layer 
  in 
  

   results 
  cited 
  aoove 
  with 
  diffusion 
  of 
  silver 
  against 
  a 
  weaker 
  

   solution 
  of 
  chromate. 
  (See 
  figs. 
  1 
  and 
  2.) 
  It 
  is 
  possible, 
  how- 
  

  

  Fig. 
  1. 
  

  

  

  -XsYHvysV'V,.-. 
  - 
  

  

  Fig. 
  1. 
  xf. 
  The 
  result 
  of 
  diffusion 
  of 
  GN 
  silver 
  nitrate 
  into 
  a 
  gelatine 
  

   containing 
  N/200 
  potassium 
  chromate. 
  The 
  drop 
  is 
  surrounded 
  by 
  an 
  area 
  

   of 
  apparently 
  continuous 
  precipitate, 
  which 
  actually 
  shows 
  fine 
  bands 
  on 
  its 
  

   surface. 
  This 
  passes 
  outwards 
  into 
  the 
  zone 
  in 
  which 
  the 
  bands 
  are 
  clearly 
  

   separated, 
  and 
  become 
  more 
  widely 
  spaced. 
  Outside 
  this 
  zone 
  is 
  a 
  non- 
  

   banded 
  zone 
  of 
  granular 
  precipitate, 
  beyond 
  this 
  a 
  zone 
  of 
  granular 
  precipi- 
  

   tate 
  arranged 
  in 
  evenly 
  spaced 
  bands. 
  This 
  is 
  followed 
  by 
  a 
  clear 
  ''halo." 
  

   It 
  is 
  probable 
  that 
  the 
  potassium 
  chromate 
  may 
  not 
  have 
  been 
  thoroughly 
  

   mixed 
  with 
  the 
  gelatine 
  so 
  as 
  to 
  give 
  uniform 
  conditions. 
  At 
  one 
  point 
  the 
  

   non-banded 
  zone 
  is 
  crossed 
  by 
  a 
  narrow 
  strip 
  of 
  bands. 
  This 
  is 
  doubtless 
  

   due 
  to 
  the 
  presence 
  of 
  a 
  streak 
  of 
  gelatine 
  richer 
  in 
  potassium 
  chromate 
  than 
  

   the 
  rest. 
  The 
  unequal 
  extensions 
  in 
  a 
  radial 
  direction 
  of 
  the 
  inner 
  banded 
  

   zone 
  may 
  be 
  explained 
  in 
  a 
  similar 
  manner. 
  

  

  