﻿Chemistry 
  and 
  Physics. 
  419 
  

  

  quartz 
  tube 
  was 
  not 
  far 
  from 
  the 
  diagonal 
  end 
  electrode 
  of 
  the 
  

   mercury 
  lamp, 
  while 
  the 
  exposed 
  end 
  of 
  the 
  quartz 
  tube 
  pro- 
  

   jected 
  some 
  distance 
  beyond 
  the 
  region 
  of 
  sealing. 
  Crystals 
  of 
  

   iodine 
  were 
  placed 
  in 
  the 
  quartz 
  tube 
  and 
  the 
  latter 
  was 
  then 
  

   highly 
  exhausted 
  by 
  the 
  aid 
  of 
  a 
  side 
  tube, 
  which 
  was 
  eventually 
  

   sealed 
  off. 
  Consequently, 
  when 
  the 
  mercury 
  lamp 
  was 
  running, 
  

   the 
  iodine 
  was 
  simultaneously 
  vaporized 
  and 
  illuminated 
  by 
  the 
  

   very 
  intense 
  source 
  of 
  radiation. 
  Negatives 
  of 
  the 
  light 
  emerg- 
  

   ing 
  from 
  the 
  outer 
  end 
  of 
  the 
  silica 
  tube 
  were 
  taken 
  with 
  a 
  quartz 
  

   spectrograph. 
  

  

  In 
  addition 
  to 
  the 
  ordinary 
  mercury 
  lines 
  coming 
  from 
  the 
  arc 
  

   in 
  the 
  outer 
  tube 
  the 
  spectrum 
  contained 
  80 
  narrow 
  bands, 
  the 
  

   mean 
  wave-lengths 
  of 
  the 
  extreme 
  bands 
  being 
  4608 
  A.U. 
  and 
  

   2129 
  A.U. 
  Although 
  the 
  new 
  spectrum 
  could 
  be 
  photographed 
  

   in 
  less 
  than 
  3 
  minutes, 
  the 
  best 
  negatives 
  were 
  obtained 
  with 
  an 
  

   exposure 
  of 
  one 
  hour. 
  Doubling 
  the 
  latter 
  interval 
  did 
  not 
  bring 
  

   out 
  anything 
  additional. 
  The 
  following 
  characteristics 
  of 
  the 
  

   spectrum 
  may 
  be 
  of 
  interest. 
  From 
  A 
  4608 
  to 
  A 
  3365 
  the 
  bands 
  

   are 
  faint 
  in 
  places 
  and 
  the 
  grouping 
  is 
  somewhat 
  irregular. 
  The 
  

   seven 
  bands 
  between 
  3315 
  and 
  3175 
  are 
  particularly 
  well-marked 
  

   and 
  appear 
  to 
  be 
  equally 
  spaced 
  at 
  intervals 
  of 
  about 
  24 
  A.U. 
  

   There 
  are 
  four 
  well-clefined 
  pairs 
  of 
  bands 
  in 
  the 
  region 
  between 
  

   3065 
  and 
  2915. 
  From 
  2900 
  to 
  2545 
  the 
  bands 
  are 
  quite 
  distinct, 
  

   but 
  the 
  spacing 
  is 
  irregular. 
  The 
  bands 
  of 
  shorter 
  wave-length 
  

   than 
  2515 
  are 
  spaced 
  about 
  20 
  A.U. 
  apart 
  and 
  each 
  band 
  is 
  about 
  

   10 
  A.U. 
  wide. 
  

  

  In 
  order 
  to 
  show 
  that 
  the 
  new 
  spectrum 
  was 
  due 
  to 
  iodine, 
  the 
  

   inner 
  tube 
  was 
  thoroughly 
  washed 
  out 
  with 
  methyl 
  alcohol, 
  

   dried, 
  etc., 
  and 
  a 
  "blank" 
  exposure 
  was 
  taken. 
  The 
  mercury 
  

   spectrum 
  then 
  came 
  out 
  very 
  strong 
  but 
  not 
  the 
  slightest 
  trace 
  

   of 
  the 
  bands 
  could 
  be 
  detected. 
  Several 
  other 
  tests 
  were 
  made 
  

   but 
  the 
  band 
  spectrum 
  could 
  only 
  be 
  obtained 
  when 
  iodine 
  vapor 
  

   was 
  present. 
  In 
  order 
  to 
  get 
  an 
  idea 
  of 
  the 
  region 
  of 
  wave- 
  

   lengths 
  in 
  the 
  mercury 
  radiation 
  which 
  excited 
  the 
  resonance 
  

   bands, 
  the 
  fused-quartz 
  tube 
  was 
  replaced 
  by 
  an 
  equal 
  length 
  of 
  

   glass 
  combustion 
  tubing 
  closed 
  at 
  the 
  outer 
  end 
  by 
  a 
  plate 
  of 
  

   crystalline 
  quartz. 
  With 
  this 
  apparatus 
  the 
  bands 
  could 
  not 
  be 
  

   photographed 
  although 
  the 
  mercury 
  lines 
  came 
  out 
  quite 
  dis- 
  

   tinctly 
  up 
  toA2893 
  , 
  7. 
  " 
  This 
  interesting 
  result 
  shows, 
  in 
  the 
  

   first 
  place, 
  that 
  the 
  emission 
  of 
  the 
  band 
  spectrum 
  by 
  the 
  iodine 
  

   vapor 
  could 
  not 
  have 
  been 
  due 
  to 
  an 
  elevation 
  of 
  the 
  tempera- 
  

   ture 
  of 
  the 
  vapor 
  by 
  the 
  heat 
  from 
  the 
  arc, 
  for 
  the 
  experimental 
  

   conditions 
  for 
  obtaining 
  a 
  temperature 
  spectrum 
  were 
  precisely 
  

   the 
  same 
  with 
  the 
  combustion 
  glass 
  tube 
  closed 
  by 
  a 
  quartz 
  win- 
  

   dow 
  as 
  w 
  T 
  ith 
  the 
  fused 
  quartz 
  tube 
  closed 
  with 
  the 
  same 
  window." 
  

   Also, 
  the 
  new 
  spectrum 
  does 
  not 
  appear 
  to 
  be 
  directly 
  related 
  to 
  

   the 
  temperature 
  band 
  spectrum 
  of 
  iodine 
  as 
  obtained 
  by 
  Konen 
  

   and 
  others. 
  It 
  is 
  thus 
  seen 
  that 
  the 
  resonance 
  bands 
  are 
  excited 
  

   by 
  radiations 
  of 
  shorter 
  wave- 
  length 
  than 
  2893 
  '1 
  A.U. 
  The 
  

   exact 
  wave-length 
  of 
  the 
  exciting 
  line 
  has 
  not 
  yet 
  been 
  deter- 
  

  

  