﻿Fox 
  Talbot's 
  Method 
  of 
  obtaining 
  Coloured 
  Flames. 
  383 
  

  

  as 
  also 
  a 
  fainter 
  line 
  on 
  the 
  more 
  refrangible 
  side 
  of 
  the 
  

   former, 
  probably 
  the 
  pair 
  at 
  X 
  5685. 
  The 
  greater 
  part 
  of: 
  

   the 
  flame, 
  although 
  more 
  intensely 
  coloured 
  than 
  without 
  

   the 
  oxygen, 
  remained, 
  however, 
  relatively 
  feeble 
  as 
  com- 
  

   pared 
  with 
  the 
  vivid 
  brightness 
  exhibited 
  by 
  the 
  immediate 
  

   vicinity 
  of 
  the 
  salt. 
  Thus 
  the 
  light 
  distribution 
  in 
  the 
  flame 
  

   is 
  not 
  very 
  uniform, 
  there 
  being 
  a 
  most 
  pronounced 
  maximum 
  

   near 
  the 
  salt. 
  

  

  In 
  addition 
  to 
  the 
  so 
  lium 
  lines 
  the 
  bands 
  of 
  the 
  Swan 
  

   spectrum 
  were 
  likewise 
  very 
  prominent 
  near 
  the 
  base 
  of 
  the 
  

   flame 
  where 
  the 
  oxygen 
  passed 
  through. 
  In 
  fact 
  the 
  path 
  of 
  

   the 
  oxygen 
  through 
  the 
  flame 
  is 
  rendered 
  visible 
  by 
  the 
  

   more 
  vigorous 
  combustion 
  of 
  unburnt 
  hydrocarbons, 
  which 
  

   gives 
  rise 
  to 
  the 
  emission 
  of 
  a 
  greenish 
  light 
  (more 
  bluish 
  

   and 
  fainter 
  w 
  r 
  hen 
  the 
  oxygen 
  passes 
  through 
  the 
  upper 
  parts 
  

   of 
  the 
  flame, 
  where 
  less 
  unburnt 
  gas 
  prevails). 
  

  

  When 
  the 
  oxygen 
  was 
  passed 
  through 
  the 
  coloured 
  region 
  

   of 
  the 
  flame 
  situated 
  just 
  above 
  the 
  salt 
  there 
  was 
  hardly 
  any 
  

   increase 
  in 
  the 
  intensity 
  of 
  the 
  light 
  emitted, 
  as 
  though 
  the 
  

   free 
  radiating 
  sodium 
  atoms 
  remained 
  unaffected 
  by 
  a 
  rise 
  in 
  

   temperature. 
  (The 
  fact 
  that 
  the 
  temperature 
  of 
  the 
  flame 
  

   is 
  appreciably 
  raised 
  by 
  the 
  oxygen 
  will 
  be 
  demonstrated 
  

  

  in 
  $. 
  2 
  -.) 
  

  

  Similar 
  results 
  were 
  obtained 
  with 
  calcium 
  chloride. 
  But 
  

   in 
  this 
  case 
  there 
  w 
  r 
  as 
  a 
  notable 
  brightening 
  of 
  the 
  spectrum 
  

   bands 
  when 
  the 
  oxygen 
  was 
  sent 
  through 
  the 
  middle 
  region 
  of 
  

   the 
  flame 
  well 
  above 
  the 
  salt. 
  This 
  may 
  be 
  due 
  to 
  undissociated 
  

   particles 
  of 
  the 
  salt 
  being 
  carried 
  upw 
  r 
  ards 
  through 
  the 
  flame 
  

   and 
  broken 
  up 
  as 
  they 
  enter 
  the 
  presumably 
  hotter 
  zone 
  of 
  

   the 
  oxygen 
  path. 
  

  

  Thallium 
  chloride 
  showed 
  no 
  line 
  when 
  placed 
  on 
  the 
  wick 
  

   of 
  the 
  spirit-lamp. 
  But 
  as 
  soon 
  as 
  oxygen 
  was 
  blown 
  against 
  

   it, 
  the 
  green 
  line 
  appeared 
  not 
  only 
  in 
  the 
  vicinity 
  of 
  the 
  

   salt 
  but 
  also 
  in 
  the 
  upper 
  part 
  of 
  the 
  flame. 
  

  

  Thus 
  it 
  is 
  evident 
  that 
  Talbot's 
  method 
  constituted 
  an 
  

   important 
  improvement 
  in 
  the 
  days 
  when 
  the 
  spirit 
  flame 
  

   was 
  practically 
  the 
  only 
  means 
  in 
  general 
  use 
  of 
  vaporizing 
  

   substances 
  for 
  spectroscopic 
  purposes. 
  

  

  2. 
  Observations 
  with 
  an 
  air-coal 
  gas 
  fiame. 
  

  

  When 
  oxygen 
  is 
  passed 
  into 
  the 
  flame 
  given 
  by 
  an 
  ordinary 
  

   Bunsen 
  or 
  Meker 
  burner, 
  there 
  is 
  a 
  great 
  tendency 
  for 
  the 
  

   former 
  to 
  strike 
  down 
  the 
  burner-tube, 
  owing 
  to 
  the 
  increased 
  

   velocity 
  of 
  the 
  explosion. 
  This 
  inconvenience 
  was 
  completely 
  

   obviated 
  by 
  placing 
  on 
  the 
  top 
  of 
  a 
  Meker 
  burner 
  a 
  perforated 
  

  

  