﻿obtaining 
  Coloured 
  Flames 
  of 
  Great 
  Intensity. 
  385 
  

  

  That 
  the 
  temperature 
  of 
  the 
  flame 
  is 
  raised 
  when 
  oxygen 
  

   is 
  passed 
  through 
  near 
  the 
  base 
  is 
  easily 
  shown 
  in 
  the 
  

   following 
  way: 
  — 
  A 
  piece 
  of 
  iron 
  wire 
  1 
  millimetre 
  thick 
  is 
  

   held 
  in 
  the 
  flame 
  about 
  half 
  way 
  up 
  from 
  the 
  burner-plate. 
  

  

  Fig. 
  2. 
  

  

  No 
  Effect. 
  

  

  In 
  this 
  position 
  it 
  will 
  be 
  raised 
  to 
  a 
  bright 
  red 
  heat. 
  If 
  now 
  

   a 
  stream 
  of 
  oxygen 
  be 
  directed 
  through 
  the 
  flame 
  just 
  above 
  

   the 
  explosion 
  region, 
  but 
  well 
  below 
  the 
  wire, 
  the 
  latter 
  

   immediately 
  becomes 
  very 
  much 
  brighter. 
  The 
  same 
  heating- 
  

   effect 
  is 
  observed 
  when 
  the 
  oxygen 
  is 
  blown 
  against 
  the 
  wire 
  

   within 
  the 
  flame. 
  

  

  Hence 
  it 
  is 
  evident 
  that 
  the 
  increased 
  intensity 
  of 
  the 
  light 
  

   emission 
  in 
  Talbot's 
  experiment 
  is 
  of 
  thermal 
  origin, 
  at 
  least 
  

   in 
  so 
  far 
  as 
  the 
  rise 
  in 
  the 
  temperature 
  of 
  the 
  flame 
  entails 
  a 
  

   more 
  vigorous 
  chemical 
  dissociation 
  of 
  the 
  salt. 
  This 
  con- 
  

   clusion 
  was 
  further 
  corroborated 
  by 
  directing 
  the 
  high- 
  

   temperature 
  flame 
  from 
  an 
  oxy-coal 
  gas 
  blowpipe 
  upon 
  the 
  

   salt 
  on 
  the 
  wick 
  of 
  the 
  spirit-lamp. 
  The 
  salt 
  in 
  this 
  case 
  gave 
  

   out 
  an 
  exceedingly 
  brilliant 
  light, 
  in 
  fact 
  much 
  more 
  so 
  than 
  

   with 
  the 
  oxygen 
  alone, 
  and 
  a 
  large 
  volume 
  of 
  luminous 
  vapour 
  

   rose 
  into 
  the 
  spirit 
  flame 
  above. 
  

  

  3. 
  Application 
  of 
  Talbot's 
  method 
  to 
  flames 
  coloured 
  by 
  

   means 
  of 
  a 
  sprayer. 
  

  

  The 
  foregoing 
  experiments 
  were 
  made 
  in 
  accordance 
  with 
  

   Talbot's 
  original 
  procedure 
  of 
  blowing 
  the 
  oxygen 
  against 
  a 
  

   lump 
  of 
  salt 
  held 
  in 
  the 
  flame. 
  But 
  the 
  method 
  is 
  equally 
  well 
  

   applicable 
  to 
  flames 
  into 
  which 
  the 
  material 
  to 
  be 
  vaporized 
  

   is 
  introduced 
  in 
  a 
  very 
  finely 
  divided 
  state, 
  such 
  as 
  is 
  provided 
  

   by 
  a 
  sprayer. 
  Also 
  in 
  this 
  case 
  it 
  was 
  found 
  that 
  the 
  greatest 
  

  

  