﻿460 
  R. 
  G. 
  Van 
  Name 
  — 
  Temperature 
  Coefficient, 
  etc. 
  

  

  coefficient. 
  This> 
  regarded 
  from 
  the 
  standpoint 
  of 
  the 
  dif- 
  

   fusion 
  theory, 
  would 
  mean 
  that 
  the 
  change 
  in 
  fluidity 
  between 
  

   0° 
  and 
  65° 
  C. 
  (an 
  increase 
  in 
  the 
  ratio 
  1 
  : 
  4) 
  has 
  no 
  appreciable 
  

   effect 
  upon 
  the 
  thickness 
  of 
  the 
  diffusion 
  layer. 
  

  

  On 
  the 
  other 
  hand, 
  it 
  is 
  at 
  least 
  equally 
  probable 
  that 
  in 
  

   reality 
  D 
  for 
  iodine 
  in 
  potassium 
  iodide 
  solution 
  increases 
  

   somewhat 
  slower 
  than 
  <f>T, 
  for 
  the 
  disturbing 
  effect 
  of 
  the 
  

   thermal 
  dissociation 
  of 
  the 
  tri-iodide 
  ion 
  would 
  act 
  in 
  this 
  

   direction, 
  as 
  is 
  evident 
  from 
  the 
  fact 
  that 
  iodine 
  diffuses 
  slower 
  

   in 
  pure 
  water 
  than 
  in 
  aqueous 
  solutions 
  of 
  potassium 
  iodide. 
  

   If 
  so, 
  the 
  rate 
  of 
  diffusion 
  must 
  increase 
  with 
  the 
  temperature 
  

   somewhat 
  more 
  slowly 
  than 
  the 
  reaction 
  velocity, 
  in 
  complete 
  

   agreement 
  with 
  the 
  predictions 
  of 
  the 
  diffusion 
  theory. 
  

  

  The 
  truth 
  or 
  falsity 
  of 
  this 
  inference 
  can 
  and 
  must 
  be 
  

   decided 
  by 
  direct 
  measurement 
  of 
  the 
  diffusion 
  coefficient 
  of 
  

   iodine 
  at 
  the 
  different 
  temperatures, 
  upon 
  the 
  values 
  of 
  which, 
  

   as 
  already 
  stated, 
  the 
  settlement 
  of 
  the 
  whole 
  question 
  turns. 
  

  

  Summary. 
  

  

  1. 
  The 
  velocity 
  of 
  the 
  reaction 
  between 
  metallic 
  cadmium 
  

   and 
  iodine, 
  dissolved 
  in 
  a 
  0'5 
  normal 
  solution 
  of 
  potassium 
  

   iodide, 
  has 
  been 
  measured 
  at 
  0°, 
  15°, 
  25°, 
  35, 
  45°, 
  55°, 
  and 
  65°, 
  

   together 
  with 
  the 
  fluidity 
  of 
  the 
  solution 
  at 
  each 
  of 
  these 
  tem- 
  

   peratures. 
  

  

  2. 
  The 
  temperature 
  coefficient 
  of 
  the 
  reaction 
  velocity 
  for 
  

   a 
  10° 
  rise 
  varies 
  from 
  1*35 
  for 
  the 
  lowest, 
  to 
  1*19 
  for 
  the 
  high- 
  

   est 
  temperature 
  interval, 
  and 
  is 
  therefore 
  of 
  about 
  the 
  same 
  

   order 
  of 
  magnitude 
  as 
  the 
  temperature 
  coefficient 
  of 
  diffusion 
  

   of 
  a 
  binary 
  electrolyte. 
  

  

  3. 
  The 
  reaction 
  velocity 
  is 
  proportional 
  to 
  the 
  product 
  of 
  

   the 
  fluidity 
  of 
  the 
  solution 
  by 
  the 
  absolute 
  temperature. 
  

  

  