﻿348 
  

  

  On 
  the 
  Absorption-Spectra 
  of 
  Metals. 
  

  

  [Mar. 
  18, 
  

  

  ments 
  we 
  observed 
  merely 
  absorption 
  in 
  the 
  blue 
  ; 
  and 
  this 
  is 
  the 
  only 
  

   case 
  in 
  which 
  the 
  effects 
  at 
  a 
  high 
  temperature 
  were 
  inferior 
  to 
  those 
  at 
  

   a 
  low 
  temperature. 
  As 
  the 
  purity 
  of 
  the 
  metal 
  first 
  employed 
  may 
  be 
  

   doubted, 
  little 
  reliance 
  can 
  be 
  placed 
  on 
  these 
  exceptional 
  results. 
  

  

  Bismuth. 
  

  

  With 
  the 
  greatest 
  thickness 
  the 
  absorption 
  of 
  bismuth 
  is 
  strikingly 
  

   similar 
  to 
  that 
  of 
  iodine 
  at 
  a 
  dull 
  red 
  heat. 
  We 
  have 
  first 
  a 
  bank 
  of 
  

   continuous 
  absorption 
  in 
  the 
  blue 
  with 
  a 
  sharp 
  boundary 
  on 
  the 
  less 
  

   refrangible 
  side, 
  and 
  then 
  a 
  channelled-space 
  absorption 
  throughout 
  the 
  

   entire 
  green 
  part 
  of 
  the 
  spectrum 
  reaching 
  to 
  D. 
  

  

  Lead. 
  

  

  This 
  metal 
  at 
  first 
  caused 
  an 
  absorption 
  at 
  both 
  ends 
  of 
  the 
  spectrum 
  ; 
  

   shortly 
  afterwards 
  the 
  whole 
  spectrum 
  was 
  extinguished. 
  As 
  this 
  is 
  a 
  

   readily 
  oxidizable 
  metal, 
  special 
  care 
  was 
  taken 
  to 
  prove 
  that 
  a 
  large 
  

   excess 
  of 
  hydrogen 
  was 
  present. 
  

  

  Thallium. 
  

  

  We 
  are 
  indebted 
  to 
  Mr. 
  Crookes 
  for 
  a 
  generous 
  supply 
  of 
  this 
  metal. 
  

   The 
  characteristic 
  green 
  line 
  of 
  thallium 
  was 
  observed 
  bright, 
  the 
  light 
  of 
  

   the 
  arc 
  not 
  being 
  reversed 
  ; 
  and 
  it 
  may 
  be 
  interesting 
  to 
  note 
  that 
  the 
  

   vapour 
  of 
  this 
  metal 
  was 
  incandescent 
  five 
  minutes 
  after 
  the 
  withdrawal 
  

   of 
  the 
  flame. 
  

  

  Gold. 
  

  

  A 
  distinct 
  absorption 
  in 
  the 
  blue 
  and 
  red 
  was 
  observed, 
  but 
  there 
  were 
  

   certainly 
  no 
  traces 
  of 
  a 
  channelled-space 
  spectrum. 
  The 
  spectral 
  lines 
  

   due 
  to 
  the 
  oxyhydrogen 
  flame 
  were 
  very 
  conspicuous. 
  It 
  may 
  be 
  noted 
  

   that 
  the 
  amount 
  of 
  gold 
  volatilized 
  was 
  only 
  0*01 
  oz. 
  ; 
  but 
  this 
  quantity 
  

   of 
  metal 
  was 
  sufficient 
  to 
  produce 
  an 
  abundant 
  supply 
  of 
  vapour. 
  

  

  Palladium. 
  

  

  This 
  metal 
  caused 
  a 
  distinct 
  absorption 
  in 
  the 
  blue, 
  but 
  no 
  effect 
  was 
  

   noticed 
  at 
  the 
  red 
  end 
  of 
  the 
  spectrum. 
  There 
  was 
  no 
  channelled-space 
  

   spectrum, 
  and 
  the 
  lines 
  caused 
  by 
  the 
  oxyhydrogen 
  flame 
  were 
  barely 
  

   visible. 
  

  

  Selenium. 
  

  

  With 
  the 
  greatest 
  thickness 
  employed 
  a 
  channelled-space 
  spectrum 
  

   was 
  given 
  by 
  selenium. 
  

  

  Iodine. 
  

  

  It 
  will 
  be 
  remembered 
  that, 
  according 
  to 
  the 
  results 
  already 
  published 
  

   by 
  one 
  of 
  us, 
  iodine 
  vapour 
  exhibits, 
  at 
  a 
  low 
  temperature, 
  a 
  channelled- 
  

   space 
  spectrum, 
  and 
  a 
  bank 
  of 
  absorption 
  in 
  the 
  violet. 
  These 
  later 
  

   experiments 
  showed 
  that, 
  at 
  the 
  more 
  elevated 
  temperature, 
  this 
  bank 
  

  

  