﻿212 
  Mr. 
  E. 
  Haigh 
  on 
  Orthobaric 
  Volumes 
  in 
  

  

  The 
  extreme 
  difference 
  between 
  the 
  values 
  of 
  2 
  is 
  reduced 
  

   by 
  this 
  change 
  from 
  '61 
  to 
  *24. 
  

  

  Whatever 
  emendation 
  equation 
  (1) 
  may 
  still 
  require, 
  it 
  is 
  

   obvious, 
  from 
  these 
  examples, 
  that 
  it 
  can 
  only 
  be 
  successfully 
  

   attempted 
  when 
  data 
  of 
  very 
  great 
  exactitude 
  are 
  available. 
  

   It 
  certainly 
  does 
  not 
  seem 
  advisable 
  to 
  modify 
  the 
  dual 
  

   equation 
  by 
  the 
  introduction 
  of 
  small 
  arbitrary 
  constants 
  

   (which 
  would 
  destroy 
  its 
  generality) 
  until 
  the 
  necessity 
  for 
  

   their 
  presence 
  has 
  been 
  more 
  fully 
  demonstrated. 
  

  

  It 
  should 
  also 
  be 
  noted 
  that 
  the 
  usual 
  integral 
  value, 
  

   — 
  273° 
  C, 
  has 
  been 
  taken 
  as 
  the 
  absolute 
  zero 
  of 
  temperature. 
  

   The 
  changes 
  in 
  the 
  value 
  of 
  6 
  which 
  would 
  be 
  produced 
  by 
  

   using 
  any 
  other 
  admissible 
  value* 
  can 
  only 
  be 
  of 
  minor 
  

   importance, 
  but 
  yet 
  are 
  not 
  quite 
  negligible, 
  at 
  temperatures 
  

   much 
  below 
  the 
  critical 
  point, 
  if 
  it 
  is 
  desired 
  to 
  arrive 
  at 
  the 
  

   closest 
  approximation 
  warranted 
  by 
  experimental 
  evidence. 
  

  

  Analogy 
  with 
  the 
  Law 
  of 
  Cailletet 
  and 
  Mathias. 
  

  

  This 
  well-known 
  law 
  expresses 
  the 
  fact 
  that 
  the 
  means 
  of 
  

   the 
  densities 
  of 
  a 
  liquid 
  and 
  its 
  saturated 
  vapour 
  are 
  a 
  linear 
  

   function 
  of 
  the 
  temperature. 
  It 
  is 
  obvious 
  from 
  its 
  form 
  

   that 
  the 
  dual 
  equation 
  may 
  be 
  similarly 
  stated. 
  

  

  Putting 
  /(0, 
  ^) 
  = 
  6. 
  F(c/>, 
  i/r) 
  and 
  

  

  equation 
  (1) 
  may 
  be 
  written 
  

  

  i. 
  e., 
  for 
  normal 
  substances, 
  the 
  means 
  of 
  the 
  values 
  of 
  the 
  

   functions 
  /'((/>, 
  -yjr) 
  and 
  f{yfr, 
  </)) 
  are 
  proportional 
  to 
  the 
  absolute 
  

   temperature. 
  

  

  Or 
  again, 
  taking 
  the 
  invariant 
  form, 
  equation 
  (3) 
  may 
  be 
  

   written 
  

  

  iiF&w 
  + 
  iXf, 
  #)}=*, 
  

  

  i.e., 
  the 
  means 
  of 
  the 
  values 
  of 
  the 
  functions 
  F' 
  v 
  0, 
  ^) 
  and 
  

   F(^, 
  <f)) 
  are 
  constant. 
  

  

  The 
  following 
  tables 
  and 
  accompanying 
  diagrams 
  ( 
  Plates 
  

   VI. 
  & 
  VII.) 
  illustrate 
  this 
  relation 
  in 
  the 
  case 
  of 
  Fluorbenzene. 
  

   As, 
  for 
  this 
  compound, 
  the 
  values 
  of 
  the 
  two 
  functions 
  are 
  

   rather 
  irregular 
  in 
  the 
  neighbourhood 
  of 
  the 
  critical 
  point, 
  a 
  

   few 
  corresponding 
  values 
  lor 
  isopentane 
  have 
  also 
  been 
  

   calculated 
  and 
  plotted 
  on 
  an 
  enlarged 
  scale. 
  

  

  * 
  Leduc 
  (Nouvelles 
  recherchea 
  aur 
  lea 
  Gcut) 
  employs 
  the 
  value 
  — 
  278 
  l'. 
  

   (The 
  following 
  note 
  has 
  been 
  kindly 
  communicated 
  by 
  Dr. 
  S. 
  Foung.) 
  

  

  I). 
  Berthelot, 
  "Sui 
  Lea 
  thermometrea 
  a 
  Gaz," 
  1 
  nnda 
  —278 
  09 
  and 
  

   E. 
  Buckingham, 
  " 
  On 
  the 
  establishment 
  of 
  the 
  thermodynamic 
  scale 
  of 
  

   temperature 
  by 
  the 
  constant 
  volume 
  thermometer/' 
  - 
  278 
  "18. 
  

  

  1 
  Travau.v 
  et 
  Mimoireadu 
  Bureau 
  International 
  des 
  Poidaet 
  Mesurea, 
  

   L908. 
  

  

  - 
  Bulletin 
  of 
  the 
  Bureau 
  of 
  Standards 
  vol. 
  iii. 
  p. 
  287 
  (Washington, 
  1907). 
  

  

  