﻿Magneto- 
  Optical 
  Rotativity. 
  365 
  

  

  red 
  side 
  o£ 
  the 
  absorption 
  band 
  and 
  decrease 
  it 
  on 
  tbe 
  violet 
  

   side. 
  If 
  this 
  is 
  tbe 
  case 
  we 
  should 
  expect 
  the 
  solid 
  dye 
  to 
  

   rotate 
  the 
  plane 
  of 
  polarization 
  for 
  waves 
  on 
  opposite 
  sides 
  

   of 
  the 
  absorption 
  band 
  in 
  opposite 
  directions. 
  The 
  author 
  

   has, 
  however, 
  been 
  unable 
  to 
  detect 
  any 
  trace 
  whatever 
  of 
  

   rotary 
  polarization 
  in 
  a 
  film 
  of 
  cyanide 
  so 
  thick 
  that 
  nothing 
  

   but 
  red 
  light 
  was 
  transmitted. 
  Saturated 
  solutions 
  of 
  

   cyanine 
  between 
  plates 
  of 
  very 
  thin 
  glass 
  also 
  showed 
  no 
  

   trace 
  of 
  the 
  phenomenon, 
  and 
  it 
  seems 
  probable 
  that 
  the 
  

   results 
  obtained 
  by 
  Schmauss 
  were 
  due 
  to 
  experimental 
  

   error." 
  

  

  It 
  can, 
  however, 
  now 
  be 
  shown 
  that 
  Wood's 
  deduction 
  

   from 
  Schmauss' 
  s 
  result 
  is 
  not 
  necessarily 
  valid, 
  and 
  that 
  the 
  

   experimental 
  facts 
  are 
  all 
  consistent. 
  Wood's 
  investigation 
  

   with 
  pure 
  cyanine 
  proves 
  that 
  there 
  is 
  no 
  appreciable 
  rota- 
  

   tion 
  due 
  to 
  that 
  substance 
  in 
  solution, 
  but 
  we 
  have 
  still 
  to 
  

   consider 
  the 
  effect 
  of 
  the 
  added 
  substance 
  on 
  the 
  rotation 
  of 
  

   the 
  alcohol. 
  A 
  modification 
  of 
  the 
  rotation 
  due 
  to 
  this 
  cause 
  

   is 
  clearly 
  indicated 
  by 
  our 
  formula, 
  and 
  is 
  of 
  precisely 
  the 
  

   same 
  kind 
  as 
  that 
  found 
  by 
  Schmauss. 
  Supposing, 
  for 
  

   simplicity, 
  that 
  the 
  added 
  cyanide 
  is 
  optically 
  effectively 
  

   equivalent 
  to 
  a 
  set 
  of 
  N-electrons 
  per 
  unit 
  volume 
  with 
  a 
  

   proper 
  frequency 
  n 
  = 
  n 
  , 
  then 
  the 
  rotation 
  of 
  the 
  light 
  of 
  

   frequency 
  n 
  would 
  be 
  modified 
  from 
  

  

  (1-aA) 
  2 
  

   to 
  G> 
  

  

  1 
  — 
  aA- 
  

  

  aNe 
  2 
  \ 
  2 
  

   m(r} 
  2 
  — 
  ri 
  2 
  )) 
  

  

  where 
  co 
  is 
  the 
  rotation 
  of 
  the 
  alcohol 
  represented 
  by 
  the 
  

   usual 
  simpler 
  form 
  of 
  Drude's 
  theory, 
  and 
  the 
  index 
  of 
  

   refraction 
  of 
  pure 
  alcohol 
  is 
  given 
  by 
  

  

  A 
  

  

  1 
  — 
  aA 
  

  

  This 
  shows 
  that 
  by 
  the 
  addition 
  of 
  the 
  cyanine 
  the 
  a> 
  is 
  

   increased 
  when 
  u<n 
  and 
  decreased 
  when 
  n>ii 
  0) 
  as 
  in 
  

   Sehmauss's 
  experiments. 
  

  

  While 
  on 
  this 
  point 
  it 
  is 
  interesting 
  to 
  notice 
  how 
  the 
  

   rotation 
  is 
  intimately 
  connected 
  with 
  the 
  refractive 
  index 
  of 
  

   the 
  medium, 
  a 
  fact 
  first 
  pointed 
  out 
  by 
  Becquerel. 
  The 
  

   formula 
  deduced 
  to 
  express 
  this 
  relation 
  does 
  not 
  appear 
  to 
  

   be 
  exact 
  when 
  the 
  influence 
  of 
  the 
  surrounding 
  medium 
  is 
  

  

  