﻿Rhythmic 
  Precipitation. 
  

  

  17 
  

  

  Thus 
  ionic 
  concentration 
  is 
  an 
  important 
  governing 
  factor 
  in 
  

   determining 
  the 
  distances 
  between 
  the 
  bands 
  of 
  precipitate. 
  

  

  Rate 
  of 
  diffusion 
  is 
  also 
  an 
  important 
  factor, 
  which 
  has 
  not 
  

   been 
  given 
  adequate 
  consideration 
  in 
  the 
  past. 
  Considering 
  

   the 
  case 
  of 
  silver 
  chromate 
  deposition, 
  the 
  rate 
  of 
  diffusion 
  of 
  

   the 
  silver 
  solution 
  is 
  greater 
  than 
  that 
  of 
  the 
  chromate 
  solution. 
  

   So 
  that, 
  after 
  the 
  formation 
  of 
  one 
  band 
  the 
  silver 
  ions 
  pass 
  

   through 
  it 
  and 
  outward 
  beyond 
  it, 
  or 
  continue 
  onward 
  from 
  

  

  Fig. 
  7, 
  

  

  few 
  

  

  

  

  • 
  

  

  

  

  

  

  

  

  

  ^r 
  o 
  

  

  

  

  

  

  

  

  

  

  

  _ 
  

  

  ■fl 
  

  

  

  

  

  ■4 
  

  

  2 
  

  

  

  >^ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  Ihr 
  

  

  Time 
  

  

  Fig. 
  7. 
  Diffusion 
  of 
  silver 
  nitrate 
  against 
  potassium 
  chromate. 
  

   I. 
  8N 
  AgN0 
  3 
  / 
  ^ 
  K 
  a 
  Cr0 
  4 
  . 
  

  

  11. 
  

  

  4N 
  

  

  AgN0 
  3 
  / 
  do 
  

  

  III. 
  

  

  2N 
  

  

  do 
  / 
  do 
  

  

  IV. 
  

  

  N 
  

  

  do 
  / 
  do 
  

  

  V. 
  

  

  N 
  

  

  do 
  / 
  ^r 
  K 
  2 
  Cr0 
  4 
  . 
  

  

  their 
  position 
  in 
  front 
  of 
  it, 
  before 
  meeting 
  the 
  chromat-ions 
  

   which 
  have 
  not 
  yet 
  crossed 
  the 
  free 
  space. 
  At 
  such 
  point 
  as 
  

   the 
  concentration 
  is 
  high 
  enough 
  to 
  give 
  labile 
  conditions 
  pre- 
  

   cipitation 
  ensues. 
  The 
  distance 
  of 
  this 
  point 
  from 
  the 
  last 
  

   formed 
  band 
  must 
  therefore 
  depend 
  upon 
  the 
  relative 
  rates 
  of 
  

   diffusion 
  of 
  the 
  two 
  solutions. 
  Thus, 
  if 
  other 
  disturbing 
  con- 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  XLIII, 
  No. 
  253. 
  — 
  January, 
  1917. 
  

  

  2 
  

  

  