﻿4 
  J. 
  Stansfield 
  — 
  Retarded 
  Diffusion 
  and 
  

  

  iron 
  chlorides 
  penetrate 
  farther, 
  perhaps 
  because 
  hydroxy! 
  ions 
  

   are 
  present. 
  Cadmium 
  chloride 
  diffuses 
  more 
  slowly 
  in 
  a 
  

   stronger 
  solution, 
  possibly 
  due 
  to 
  association. 
  

  

  By 
  diffusing 
  different 
  salts 
  of 
  silver 
  into 
  gelatines 
  contain- 
  

   ing 
  the 
  same 
  reacting 
  salts, 
  in 
  the 
  same 
  concentrations, 
  the 
  

   reactions 
  were 
  found 
  to 
  proceed 
  at 
  the 
  same 
  speed 
  regardless 
  

   of 
  the 
  combined 
  ion, 
  showing 
  that 
  the 
  silver 
  ion 
  is 
  the 
  import- 
  

   ant 
  one 
  for 
  the 
  reaction. 
  

  

  Solutions 
  of 
  potassium 
  chloride, 
  bromide 
  and 
  iodide 
  were 
  

   diffused 
  against 
  silver 
  nitrate, 
  the 
  distances 
  being 
  measured, 
  

   with 
  the 
  following 
  results 
  : 
  

  

  A 
  „D 
  T>„ 
  

  

  Ratio 
  of 
  distances 
  diffused 
  , 
  1-034 
  Yel. 
  of 
  diffusion 
  -^1-0366 
  

  

  AgCl 
  CI 
  

  

  AffBr 
  „ 
  Br 
  

  

  — 
  P^- 
  1*017 
  —1*0185 
  

  

  Agl 
  I 
  

  

  Aol 
  I 
  

  

  Agbr 
  1 
  ' 
  016 
  ' 
  cr 
  1 
  ' 
  0146 
  

  

  Other 
  cases 
  gave 
  equally 
  satisfactory 
  results, 
  while 
  some 
  gave 
  

  

  discordant 
  results. 
  

  

  Hausmann 
  thus 
  proved 
  that 
  the 
  reaction 
  depends 
  only 
  on 
  

  

  the 
  ions 
  involved 
  in 
  the 
  precipitate, 
  and 
  not 
  on 
  those 
  combined 
  

  

  with 
  them, 
  and 
  that 
  the 
  speed 
  of 
  the 
  reaction 
  depends 
  on 
  the 
  

  

  ion 
  which 
  diffuses 
  into 
  the 
  jelly 
  and 
  not 
  on 
  the 
  one 
  which 
  is 
  

  

  present 
  in 
  the 
  jelly. 
  He 
  also 
  confirmed 
  the 
  result 
  of 
  Morse 
  

  

  . 
  , 
  ... 
  distance 
  . 
  „. 
  , 
  . 
  

  

  and 
  Jrierce 
  (see 
  page 
  1) 
  that 
  -. 
  is 
  constant. 
  He 
  pointed 
  

  

  out 
  that 
  this 
  constitutes 
  the 
  first 
  non-electric 
  method 
  of 
  deter- 
  

   mining 
  diffusion 
  velocities. 
  

  

  In 
  1905 
  Bechhold 
  (6) 
  called 
  attention 
  to 
  the 
  importance 
  of 
  

   rhythmic 
  precipitation 
  in 
  the 
  development 
  of 
  layers 
  of 
  silica, 
  

   horn, 
  and 
  calcium 
  carbonate 
  in 
  sponges, 
  the 
  development 
  of 
  

   layered 
  calcareous 
  shells 
  in 
  the 
  perforated 
  Foraminifera, 
  in 
  

   gasteropod 
  and 
  lamellibranch 
  shells, 
  the 
  development 
  of 
  layers 
  

   in 
  the 
  bones 
  of 
  some 
  vertebrates, 
  and 
  its 
  importance 
  in 
  intus- 
  

   susception 
  in 
  plants. 
  

  

  Bechhold 
  agrees 
  with 
  Ostwald 
  concerning 
  the 
  super-satura- 
  

   tion 
  idea. 
  He 
  used 
  ammonium 
  chromate 
  or 
  bichromate 
  in 
  

   making 
  ring 
  precipitates 
  and 
  found 
  that 
  owing 
  to 
  the 
  fact 
  that 
  

   silver 
  chromate 
  is 
  slightly 
  soluble 
  in 
  ammonium 
  salts 
  that 
  the 
  

   bands 
  are 
  more 
  widely 
  spaced. 
  He 
  mentioned 
  the 
  strong 
  con- 
  

   tractive 
  forces 
  which 
  are 
  set 
  up 
  in 
  gelatine 
  when 
  silver 
  nitrate 
  

   is 
  added 
  to 
  it, 
  and 
  suggested 
  that 
  these 
  forces 
  may 
  have 
  some- 
  

   thing 
  to 
  do 
  with 
  the 
  formation 
  of 
  the 
  rings. 
  But 
  this 
  appears 
  

   not 
  to 
  be 
  the 
  case 
  because 
  under 
  crossed 
  nicols 
  there 
  is 
  not 
  a 
  

   maximum 
  brightness 
  between 
  the 
  bands. 
  

  

  