﻿246 
  Dr. 
  P. 
  Chappuis 
  on 
  Gas- 
  Thermometry 
  . 
  

  

  value 
  given 
  by 
  the 
  experiments 
  of 
  Messrs. 
  Holborn 
  and 
  Day 
  

   for 
  the 
  temperature 
  445°. 
  I 
  have 
  kept 
  in 
  this 
  calculation 
  

   the 
  coefficient 
  obtained 
  by 
  me 
  for 
  nitrogen 
  between 
  0° 
  and 
  

   100°. 
  

  

  It 
  follows 
  from 
  the 
  introduction 
  of 
  the 
  new 
  values, 
  that 
  the 
  

   boiling-point 
  of 
  sulphur 
  deduced 
  from 
  our 
  experiments 
  with 
  

   a 
  porcelain-reservoir 
  thermometer 
  would 
  be 
  lowered 
  C 
  *5 
  C. 
  

   from 
  445°* 
  2 
  to 
  444°' 
  7. 
  This 
  number 
  is 
  very 
  close 
  to 
  that 
  

   obtained 
  by 
  Messrs. 
  Oallendar 
  and 
  Griffiths. 
  

  

  It 
  is 
  possible 
  that 
  the 
  measurements 
  in 
  which 
  we 
  employed 
  

   a 
  reservoir 
  of 
  " 
  verre 
  dur," 
  and 
  which 
  also 
  gave 
  us 
  a 
  value 
  

   for 
  the 
  boiling-point 
  close 
  to 
  445°* 
  2, 
  may 
  be 
  affected 
  by 
  a 
  

   similar 
  error, 
  but 
  the 
  data 
  at 
  present 
  available 
  for 
  the 
  ex- 
  

   pansion 
  of 
  this 
  glass 
  at 
  high 
  temperatures 
  do 
  not 
  now 
  permit 
  

   of 
  the 
  error, 
  if 
  any, 
  being 
  calculated. 
  

  

  I 
  think 
  there 
  would 
  be 
  some 
  interest 
  in 
  redetermining 
  the 
  

   boiling-point 
  of 
  sulphur, 
  using 
  a 
  bulb 
  of 
  platinum-iridium 
  

   whose 
  expansion 
  follows 
  a 
  regular 
  and 
  better 
  known 
  law. 
  

  

  2. 
  In 
  the 
  note 
  mentioned 
  above 
  (PhiL 
  Mag. 
  [5] 
  1. 
  p. 
  431) 
  

  

  1 
  dP 
  

   I 
  gave 
  the 
  values 
  of 
  the 
  coefficient 
  ^- 
  — 
  for 
  nitrogen 
  for 
  an 
  

  

  x 
  o 
  dit 
  

  

  initial 
  pressure 
  P 
  of 
  one 
  metre, 
  at 
  different 
  temperatures 
  

   comprised 
  between 
  0° 
  and 
  100°. 
  Examination 
  of 
  the 
  table 
  

   of 
  these 
  values 
  shows 
  that 
  the 
  coefficient 
  of 
  nitrogen 
  gradually 
  

   diminishes 
  and 
  reaches 
  near 
  75° 
  a 
  limiting 
  value 
  equal 
  to 
  

  

  * 
  lim 
  = 
  0-003 
  673 
  80. 
  

  

  It 
  may 
  be 
  assumed 
  that 
  starting 
  from 
  this 
  temperature 
  the 
  

   gas 
  is 
  in 
  the 
  perfect 
  state. 
  . 
  

  

  Direct 
  observations 
  of 
  the 
  constants 
  of 
  the 
  nitrogen 
  ther- 
  

   mometer 
  having 
  given 
  

  

  P 
  = 
  1-000 
  000 
  m. 
  and 
  P 
  100 
  = 
  1*367 
  466 
  m., 
  

  

  we 
  may 
  deduce 
  the 
  initial 
  pressure 
  P 
  ', 
  which 
  should 
  have 
  

   been 
  observed 
  had 
  the 
  nitrogen 
  retained 
  down 
  to 
  0° 
  the 
  

   properties 
  of 
  a 
  perfect 
  gas 
  ; 
  that 
  is 
  to 
  say, 
  if 
  the 
  pressure 
  had 
  

   continued 
  to 
  vary 
  from 
  100° 
  downwards 
  at 
  the 
  rate 
  of 
  

   0*003 
  673 
  80 
  metre 
  per 
  degree. 
  

   We 
  should 
  then 
  have 
  

  

  P 
  ' 
  = 
  P 
  100 
  -0-003 
  673 
  80 
  x 
  100 
  = 
  1-000 
  086 
  m. 
  

  

  The 
  thermometer 
  supposed 
  perfect 
  would 
  therefore 
  have 
  at 
  0° 
  

   the 
  pressure 
  P 
  ' 
  = 
  1*000086 
  m. 
  and 
  at 
  100° 
  P 
  100 
  = 
  1*367 
  466 
  m., 
  

  

  