﻿136 
  Uhler 
  and 
  Patterson 
  — 
  Arc 
  Spectrum 
  of 
  Tellurium. 
  

  

  up 
  by 
  one 
  of 
  us 
  to 
  obtain 
  the 
  data 
  for 
  the 
  " 
  Atlas 
  of 
  Absorp- 
  

   tion 
  Spectra"*. 
  The 
  larger 
  grating 
  has 
  a 
  radius 
  of 
  curvature 
  

   of 
  about 
  21*5 
  feet 
  and 
  15,000 
  lines 
  per 
  inch. 
  It 
  is 
  mounted 
  

   according 
  to 
  Rowland's 
  plan. 
  With 
  these 
  two 
  spectrographs 
  

   we 
  have 
  been 
  able 
  to 
  test 
  Flint's 
  material 
  successfully 
  and 
  to 
  

   investigate 
  the 
  arc 
  spectrum 
  of 
  tellurium. 
  The 
  latter 
  problem 
  

   being 
  the 
  more 
  important 
  and 
  fruitful 
  will 
  be 
  taken 
  up 
  first. 
  

  

  With 
  the 
  smaller 
  instrument 
  films 
  sensitized 
  by 
  the 
  " 
  Pan- 
  

   chromatic 
  B" 
  emulsion 
  of 
  Wratten 
  and 
  Wainwright 
  were 
  

   used. 
  We 
  found 
  these 
  films 
  to 
  be 
  uniformly 
  sensitive 
  from 
  

   about 
  X 
  2300 
  to 
  X 
  6500. 
  With 
  long 
  exposures 
  or 
  with 
  very 
  

   intense 
  radiations 
  it 
  was 
  possible 
  to 
  photograph 
  between 
  the 
  

   limits 
  X 
  2000 
  and 
  X 
  7200. 
  With 
  the 
  larger 
  apparatus 
  Cramer 
  

   "Crown" 
  and 
  "Instantaneous 
  Isochromatic 
  " 
  plates 
  were 
  

   employed. 
  The 
  simple 
  hydrochinone 
  developer 
  as 
  formulated 
  

   by 
  Jewell 
  was 
  used 
  throughout. 
  

  

  When 
  the 
  work 
  was 
  begun 
  we 
  could 
  only 
  find 
  four 
  arc 
  lines 
  

   of 
  tellurium 
  recorded. 
  These 
  were 
  measured 
  by 
  Exner 
  and 
  

   Haschek. 
  When 
  the 
  sixth 
  volume 
  of 
  Kayser's 
  " 
  Handbuch 
  

   der 
  Spectroscopic 
  " 
  reached 
  us 
  it 
  added 
  three 
  more 
  arc 
  lines, 
  

   as 
  determined 
  by 
  Eder 
  and 
  Yalenta. 
  These 
  seven 
  lines 
  are 
  all 
  

   in 
  the 
  ultra-violet 
  above 
  X 
  2800 
  and 
  yet 
  the 
  arc 
  produced 
  by 
  

   bringing 
  in 
  contact 
  and 
  quickly 
  separating 
  two 
  rods 
  of 
  metallic 
  

   tellurium 
  is 
  so 
  intensely 
  bright 
  as 
  to 
  suggest 
  the 
  existence 
  of 
  

   radiations 
  in 
  the 
  visible 
  region 
  of 
  the 
  spectrum. 
  The 
  hypo- 
  

   thesis 
  that 
  this 
  light 
  was 
  due 
  entirely 
  to 
  incandescent 
  solid 
  or 
  

   liquid 
  tellurium 
  did 
  not 
  seem 
  adequate. 
  For 
  this 
  reason, 
  as 
  

   well 
  as 
  on 
  account 
  of 
  the 
  fact 
  that 
  certain 
  articles 
  in 
  chemical 
  

   journals 
  imply 
  that 
  some 
  of 
  the 
  tellurium 
  lines 
  coincide 
  exactly 
  

   with 
  the 
  lines 
  of 
  other 
  elements, 
  we 
  decided 
  to 
  investigate 
  the 
  

   arc 
  spectrum 
  as 
  if 
  nothing 
  were 
  known 
  about 
  it 
  in 
  advance. 
  

   The 
  problem 
  consisted, 
  therefore, 
  in 
  two 
  parts, 
  first, 
  the 
  deter- 
  

   mination 
  of 
  all 
  the 
  lines 
  which 
  pertain 
  to 
  the 
  arc 
  spectrum 
  of 
  

   tellurium 
  and 
  only 
  to 
  this 
  substance 
  and, 
  second, 
  the 
  measure- 
  

   ment 
  of 
  the 
  wave-lengths 
  of 
  the 
  arc 
  lines 
  in 
  terms 
  of 
  the 
  inter- 
  

   ferometer 
  standards. 
  

  

  Obviously, 
  the 
  meter-radius 
  grating 
  was 
  employed 
  to 
  attack 
  

   the 
  first 
  part 
  of 
  the 
  problem. 
  To 
  have 
  a 
  sure 
  foundation 
  of 
  

   comparison, 
  negatives 
  were 
  taken 
  of 
  the 
  arc 
  spectra 
  of 
  all 
  the 
  

   metals, 
  17 
  in 
  number, 
  which 
  were 
  likely 
  to 
  occur 
  as 
  impurities 
  

   in 
  the 
  metallic 
  tellurium 
  or 
  in 
  the 
  oxides 
  and 
  nitrates 
  of 
  this 
  

   element. 
  Selenium 
  does 
  not 
  give 
  an 
  arc 
  spectrum 
  and 
  

   hence 
  it 
  presents 
  no 
  difficulty 
  as 
  far 
  as 
  the 
  lines 
  of 
  tel- 
  

   lurium 
  are 
  concerned. 
  On 
  the 
  other 
  hand, 
  selenium 
  affords 
  

   an 
  example 
  of 
  a 
  substance 
  which 
  would 
  escape 
  detection 
  

   if 
  the 
  arc 
  alone 
  were 
  used 
  in 
  analyzing 
  spectroscopically 
  

  

  *H. 
  S. 
  Uhler 
  and 
  E. 
  W. 
  Wood, 
  Carnegie 
  Publication 
  No. 
  71 
  (1907). 
  

  

  