﻿High 
  Temperatures. 
  1Y3 
  

  

  Heating 
  arrangements. 
  — 
  For 
  all 
  the 
  observations 
  with 
  the 
  

   ^lass 
  bulb 
  a 
  nitre 
  bath 
  was 
  used, 
  heated 
  by 
  Bunsen 
  burners. 
  

   The 
  bath 
  was 
  contained 
  in 
  a 
  cast 
  iron 
  kettle 
  34'^°^ 
  high 
  and 
  18^™ 
  

   in 
  diameter, 
  provided 
  with 
  a 
  cover 
  through 
  which 
  the 
  ther- 
  

   mometer 
  bulb 
  and 
  the 
  porcelain 
  tubes 
  containing 
  the 
  thermo- 
  

   element 
  were 
  passed, 
  the 
  whole 
  being 
  protected 
  from 
  radiation 
  

   bj 
  a 
  thick 
  outer 
  cylinder 
  of 
  fire-clay. 
  The 
  bath 
  was 
  stirred 
  

   continually 
  by 
  a 
  turbine 
  wheel 
  driven 
  from 
  outside. 
  Inasmuch 
  

   as 
  the 
  bath 
  when 
  cold 
  solidified, 
  the 
  kettle 
  was 
  first 
  heated 
  to 
  

   250° 
  empty 
  and 
  the 
  previously 
  melted 
  nitre 
  poured 
  in 
  through 
  

   a 
  funnel. 
  At 
  the 
  close 
  of 
  the 
  day's 
  measurements 
  the 
  nitre 
  

   was 
  drawn 
  ojff 
  while 
  still 
  hot 
  with 
  a 
  siphon. 
  

  

  Hydrogen. 
  — 
  The 
  hydrogen 
  used 
  was 
  generated 
  electrolyti- 
  

   cally 
  from 
  dilute 
  sulphuric 
  acid, 
  and 
  before 
  being 
  admitted 
  into 
  

   the 
  bulb 
  was 
  passed 
  through 
  two 
  wash 
  bottles 
  containing 
  alka- 
  

   line 
  solution 
  of 
  pyrogallic 
  acid 
  to 
  remove 
  traces 
  of 
  oxygen 
  

   present, 
  and 
  drying 
  tubes 
  containing 
  calcium 
  chloride 
  and 
  phos- 
  

   phoric 
  pentoxide. 
  Failure 
  to 
  take 
  this 
  precaution 
  always 
  

   resulted 
  in 
  a 
  fall 
  of 
  the 
  ice 
  point 
  after 
  heating, 
  amounting 
  to 
  

   from 
  3 
  to 
  5"^™ 
  mercury 
  pressure. 
  This 
  difference 
  diminished 
  

   with 
  subsequent 
  heatings 
  (the 
  heatings 
  were 
  each 
  about 
  five 
  

   hours 
  long), 
  as 
  may 
  be 
  seen 
  in 
  the 
  following 
  instance 
  : 
  

  

  Gas 
  pressure 
  at 
  0°. 
  

  

  Bulb 
  freshly 
  filled 
  567-80"^°^ 
  Hg. 
  

  

  Alter 
  Ist 
  heating 
  (to 
  510°) 
  564-63 
  " 
  • 
  

  

  " 
  2d 
  " 
  "530 
  564''15 
  " 
  

  

  '* 
  3d 
  " 
  " 
  500 
  563-61 
  " 
  

  

  '' 
  4th 
  '' 
  '' 
  540 
  562-83 
  " 
  

  

  " 
  5th 
  " 
  " 
  540 
  562-56 
  " 
  

  

  The 
  phenomenon 
  is 
  to 
  be 
  attributed 
  to 
  a 
  gradual 
  combining 
  

   of 
  the 
  hydrogen 
  with 
  the 
  oxygen 
  present 
  and 
  occurs 
  even 
  

   when 
  the 
  temperature 
  is 
  not 
  carried 
  above 
  400°. 
  Before 
  the 
  

   final 
  filling 
  the 
  bulb 
  was 
  always 
  evacuated 
  at 
  a 
  temperature 
  of 
  

   500° 
  and 
  allowed 
  to 
  stand 
  for 
  several 
  hours, 
  being 
  "rinsed" 
  

   from 
  time 
  to 
  time 
  with 
  dry 
  hydrogen. 
  The 
  generating 
  appara- 
  

   tus 
  and 
  connections 
  were 
  perfectly 
  air-tight 
  and 
  remained 
  so 
  

   throughout. 
  

  

  Expansion 
  of 
  Bulb. 
  — 
  For 
  the 
  glass 
  bulb 
  3/3 
  is 
  assumed 
  

   equal 
  to 
  0*000018,^ 
  a 
  value 
  determined 
  for 
  the 
  temperature 
  

   range 
  0°-100°. 
  The 
  " 
  unheated 
  space" 
  affects 
  the 
  result 
  {t) 
  

   2-6 
  per 
  cent 
  at 
  200° 
  and 
  4-1 
  per 
  cent 
  at 
  500°. 
  

  

  *Thiesen, 
  Scheel 
  and 
  Sell, 
  Wissensch. 
  Abhandl. 
  d. 
  Phys.-Tech. 
  Reichsanstalt, 
  

   ii, 
  129, 
  1895. 
  

  

  