﻿166 
  Holhorn 
  and 
  Bay 
  — 
  Gas 
  Thermometer 
  at 
  

  

  With 
  the 
  idea 
  that 
  these 
  differences 
  were, 
  in 
  part 
  at 
  least, 
  

   due 
  to 
  the 
  construction 
  and 
  handling 
  of 
  the 
  gas 
  thermometer 
  

   itself, 
  the 
  first 
  step 
  toward 
  the 
  establishment 
  of 
  a 
  new 
  scale 
  

   was 
  thought 
  to 
  lie 
  in 
  the 
  direction 
  of 
  an 
  investigation 
  of 
  the 
  

   principal 
  instrument 
  involved. 
  The 
  results 
  of 
  such 
  an 
  investi- 
  

   gation 
  are 
  contained 
  in 
  this 
  paper. 
  

  

  There 
  is 
  no 
  doubt 
  that 
  the 
  principal 
  difficulty 
  lies 
  imme- 
  

   diately 
  at 
  hand, 
  viz., 
  in 
  providing 
  a 
  suitable 
  bulb 
  to 
  hold 
  the 
  

   expanding 
  gas. 
  Since 
  Deville 
  and 
  Troost"^ 
  proved 
  that 
  hydro- 
  

   gen 
  would 
  pass 
  through 
  the 
  walls 
  of 
  a 
  platinum 
  bulb 
  at 
  high 
  

   temperatures, 
  observers 
  in 
  general 
  have 
  turned 
  to 
  porcelain 
  as 
  

   the 
  onlj 
  practicable 
  material, 
  although 
  the 
  results 
  obtained 
  by 
  

   Becquerelf 
  with 
  the 
  Pouillet 
  platinum 
  bulbs 
  compare 
  by 
  no 
  

   means 
  so 
  unfavorably 
  with 
  the 
  determinations 
  above 
  quoted, 
  

   and 
  the 
  discrepancy 
  between 
  the 
  Becquerel 
  values 
  and 
  those 
  

   obtained 
  at 
  about 
  the 
  same 
  time 
  by 
  Deville 
  and 
  Troost 
  was 
  suffi- 
  

   ciently 
  explained 
  by 
  the 
  dissociation 
  of 
  the 
  gas 
  (iodine 
  vapor) 
  

   chosen 
  for 
  the 
  observations. 
  

  

  Among 
  recent 
  observers 
  Yiolle, 
  following 
  the 
  precedent 
  of 
  

   Deville 
  and 
  Troost, 
  used 
  porcelain 
  bulbs 
  glazed 
  inside 
  and 
  out, 
  

   while 
  Barus, 
  as 
  well 
  as 
  Holborn 
  and 
  Wien, 
  adopted 
  those 
  

   glazed 
  only 
  on 
  the 
  outside. 
  The 
  limits 
  of 
  usefulness 
  of 
  the 
  

   bulbs 
  with 
  inside 
  glazing 
  nnust 
  be 
  reached 
  when 
  the 
  glaze 
  

   begins 
  to 
  melt, 
  i. 
  e. 
  at 
  about 
  1100°, 
  otherwise 
  vaporization 
  is 
  

   certainly 
  to 
  be 
  feared. 
  The 
  porcelain 
  walls 
  themselves 
  hold 
  

   out 
  longer, 
  in 
  fact 
  the 
  bulbs 
  without 
  inside 
  glazing 
  used 
  by 
  

   Holborn 
  and 
  Wien 
  were 
  used 
  up 
  to 
  1450°, 
  but 
  of 
  coarse 
  

   at 
  such 
  a 
  temperature 
  the 
  pressure 
  inside 
  and 
  out 
  must 
  be 
  

   approximately 
  the 
  same, 
  that 
  the 
  already 
  soft 
  walls 
  may 
  not 
  

   be 
  deformed 
  thereby. 
  At 
  these 
  temperatures 
  porcelain 
  bulbs 
  

   only 
  remain 
  air-tight 
  by 
  virtue 
  of 
  the 
  glazing 
  — 
  unglazed 
  pdi'ce- 
  

   lain 
  is 
  not 
  air-tight. 
  

  

  Brief 
  revieiv 
  of 
  investigation. 
  — 
  Our 
  experiments 
  uj) 
  to 
  a 
  

   temperature 
  of 
  550° 
  were 
  made 
  with 
  bulbs 
  of 
  Jena 
  " 
  borosili- 
  

   cate 
  " 
  glass 
  No. 
  59"^ 
  and 
  hydrogen 
  as 
  the 
  expanding 
  gas; 
  then 
  

   porcelain 
  bulbs 
  glazed 
  inside 
  and 
  out 
  were 
  tried 
  up 
  to 
  1100°, 
  

   first 
  with 
  hydrogen 
  and 
  afterwards 
  with 
  atmospheric 
  nitrogen 
  ; 
  

   next 
  porcelain 
  bulbs 
  with 
  outside 
  glazing 
  only 
  were 
  heated 
  

   above 
  1200° 
  with 
  nitrogen 
  ; 
  and 
  finally 
  a 
  platin-iridium 
  bulb, 
  

   which 
  when 
  heated 
  electrically 
  proved 
  entirely 
  free 
  from 
  the 
  

   disadvantages 
  of 
  porcelain, 
  was 
  used 
  with 
  chemically 
  pure 
  

   nitrogen 
  over 
  the 
  whole 
  range 
  of 
  temperature 
  up 
  to 
  1300°. 
  

  

  Toward 
  the 
  close 
  of 
  the 
  observations 
  we 
  also 
  had 
  the 
  advan- 
  

   tage 
  of 
  entirely 
  new 
  manometric 
  apparatus 
  especially 
  adapted 
  to 
  

   our 
  purposes, 
  in 
  which 
  the 
  volume 
  of 
  unheated 
  gas 
  was 
  much 
  

   reduced 
  and 
  the 
  use 
  of 
  low 
  pressures 
  in 
  the 
  bulb 
  made 
  possible. 
  

  

  * 
  De\Mlle 
  and 
  Troost, 
  C. 
  R.. 
  Ivi, 
  977, 
  18G3. 
  

  

  f 
  E. 
  Becquerel, 
  Ann. 
  de 
  Chira. 
  et 
  de 
  Phys., 
  Ill, 
  Ixviii, 
  49, 
  1862. 
  

  

  