﻿Properties 
  of 
  Films 
  of 
  Magnetic 
  Metals. 
  

  

  857 
  

  

  differential 
  absorption 
  coefficient 
  (k 
  r 
  — 
  h) 
  was 
  not 
  the 
  same 
  

   in 
  the 
  two 
  films. 
  

  

  The 
  coefficients 
  of 
  extinction 
  and 
  the 
  refractive 
  indices 
  of 
  

   these 
  films 
  are 
  also 
  given 
  in 
  Table 
  XIV. 
  and 
  plotted 
  in 
  fig. 
  12. 
  

   The 
  extinction 
  is 
  much 
  less 
  than 
  that 
  of 
  dark 
  iron, 
  and 
  also 
  

   increases 
  much 
  less 
  rapidly 
  with 
  decreasing 
  wave-lengths. 
  

   The 
  refractive 
  index 
  rises 
  very 
  slightly 
  in 
  passing 
  from 
  red 
  

   to 
  blue. 
  

  

  13. 
  Electrolytic 
  Cobalt. 
  

  

  Films 
  o£ 
  electrolytic 
  cobalt 
  were 
  deposited 
  on 
  platinized 
  

   glass 
  from 
  a 
  solution 
  of 
  cobalt-ammonium-sulphate. 
  They 
  

   proved 
  remarkably 
  more 
  active 
  in 
  a 
  magnetic 
  field 
  than 
  those 
  

   of 
  Lobach 
  (I. 
  c). 
  Our 
  experience 
  showed 
  that 
  the 
  concen- 
  

   tration 
  of 
  the 
  solution 
  and 
  the 
  rate 
  of 
  deposit 
  affects 
  the 
  

   hardness 
  of 
  the 
  electrolytic 
  films 
  of 
  both 
  iron 
  and 
  cobalt, 
  and 
  

   we 
  are 
  inclined 
  to 
  believe 
  that 
  it 
  also 
  affects 
  their 
  magnetic 
  

   activity 
  as 
  well, 
  though 
  this 
  was 
  not 
  tested. 
  These 
  films 
  

   hold 
  less 
  closely 
  to 
  a 
  definite 
  type 
  than 
  either 
  the 
  dark 
  or 
  

   the 
  metallic 
  films. 
  

  

  Two 
  thick 
  films 
  were 
  produced 
  for 
  the 
  purpose 
  of 
  obtaining 
  

   their 
  rotatory 
  power 
  for 
  the 
  brightest 
  region 
  of 
  the 
  spectrum. 
  

   The 
  measurements 
  are 
  given 
  in 
  the 
  following 
  table. 
  

  

  Table 
  XV. 
  

   Wave-length, 
  520 
  /*/*. 
  Field, 
  13,600 
  c.G.s. 
  

  

  Film. 
  

  

  Thickness 
  X 
  10 
  7 
  (cm.). 
  

  

  Kotation. 
  

  

  Rotation 
  

   Thickness* 
  

  

  Pt 
  + 
  Co. 
  

  

  Pt. 
  (approx.). 
  

  

  Co. 
  

  

  30 
  

   32 
  

  

  76 
  

   66 
  

  

  6 
  

   6 
  

  

  70 
  

   60 
  

  

  2-31 
  

   1-80 
  

  

  330,000 
  

   300,000 
  

  

  The 
  mean 
  of 
  these 
  values 
  of 
  the 
  rotation 
  divided 
  by 
  the 
  

   thickness 
  was 
  used 
  for 
  determining 
  the 
  thickness 
  of 
  the 
  other 
  

   films 
  studied. 
  

  

  Table 
  XVI. 
  contains 
  results 
  from 
  film 
  31 
  possessing 
  a 
  

   thickness 
  of 
  31 
  x 
  10~ 
  7 
  cm. 
  The 
  quantitative 
  results 
  from 
  

   different 
  films 
  did 
  not 
  agree 
  well 
  enough 
  to 
  warrant 
  a 
  more 
  

   extended 
  study, 
  especially 
  in 
  reference 
  to 
  their 
  elliptic 
  

   polarization. 
  Two 
  films 
  as 
  measured 
  gave 
  the 
  same 
  value 
  

   for 
  ellipticity 
  while 
  their 
  rotation 
  differed 
  by 
  more 
  than 
  

   thirty 
  per 
  cent. 
  The 
  results 
  from 
  film 
  31 
  are, 
  however, 
  

   typical 
  as 
  regards 
  the 
  variation 
  with 
  wave-length. 
  The 
  curves 
  

  

  