﻿222 
  Mr. 
  E. 
  Haigh 
  on 
  Orthobaric 
  Volumes 
  in 
  

  

  the 
  result. 
  Provided, 
  however, 
  that 
  the 
  substance 
  is 
  fairly 
  

   normal 
  and 
  that 
  an 
  adequate 
  length 
  of 
  the 
  mean-density 
  me 
  

   has 
  been 
  experimentally 
  constructed, 
  it 
  is 
  very 
  unlikely 
  that 
  

   the 
  point 
  representing 
  the 
  critical 
  density 
  will 
  he 
  on 
  the 
  

   same 
  side 
  of 
  all 
  the 
  lines 
  so 
  obtained. 
  Hence 
  a 
  useful 
  

   indication 
  will 
  be 
  afforded 
  of 
  the 
  limits 
  within 
  which 
  the 
  

   true 
  critical 
  volume 
  will 
  most 
  probably 
  lie 
  even 
  when 
  

   experimental 
  investigation 
  in 
  the 
  neighbourhood 
  ol 
  the 
  

   critical 
  point 
  is 
  not 
  feasible. 
  m 
  

  

  To 
  Dr 
  S 
  Youno- 
  (to 
  whom 
  the 
  first 
  manuscript 
  copy 
  ot 
  

   this 
  article 
  was 
  sent), 
  1 
  desire 
  here 
  to 
  tender 
  very 
  cordial 
  

   thanks 
  for 
  the 
  helpful 
  notes 
  and 
  criticism 
  with 
  which 
  he 
  has 
  

   favoured 
  me 
  whilst 
  preparing 
  this 
  paper 
  for 
  publication 
  

   I 
  am 
  also 
  indebted 
  to 
  Mr. 
  A. 
  G. 
  Wilkinson 
  for 
  careful 
  

   clerical 
  assistance. 
  

  

  Note 
  hj 
  Sydney 
  Young, 
  D.Sc., 
  F.R.S., 
  

  

  Trinity 
  College, 
  Dublin. 
  

  

  The 
  proofs 
  of 
  the 
  correctness 
  of 
  his 
  "dual" 
  equation 
  

   which 
  Mr. 
  Haigh 
  has 
  brought 
  forward 
  appear 
  to 
  be 
  very 
  

   complete 
  and 
  satisfactory, 
  and 
  it 
  is 
  probable 
  that 
  some, 
  

   though 
  not 
  all, 
  of 
  the 
  deviations 
  of 
  the 
  calculated 
  values 
  

   of 
  2* 
  from 
  the 
  theoretical 
  value, 
  16, 
  may 
  be 
  due 
  to 
  ex- 
  

   perimental 
  errors. 
  . 
  , 
  

  

  It 
  may 
  be 
  pointed 
  out 
  that 
  such 
  errors 
  are 
  111 
  general 
  

   most 
  likely 
  to 
  occur 
  in 
  the 
  determinations 
  of 
  the 
  volumes 
  

   of 
  saturated 
  vapour 
  at 
  the 
  lower 
  temperatures, 
  and 
  it 
  is 
  

   probable 
  that 
  the 
  single 
  rather 
  large 
  deviation 
  111 
  the 
  case 
  

   of 
  normal 
  pentane 
  at 
  the 
  lowest 
  temperature 
  may 
  be 
  ex- 
  

   plained 
  in 
  this 
  way. 
  The 
  results 
  with 
  rc-pentane 
  should 
  be 
  

   specially 
  accurate, 
  and 
  the 
  greatest 
  of 
  the 
  remaining 
  devia- 
  

   tions, 
  0-07, 
  is 
  small. 
  Omitting 
  the 
  first 
  result, 
  the 
  mean 
  

   value 
  of 
  2 
  would 
  be 
  15*965 
  instead 
  of 
  15-9,). 
  _ 
  

  

  Serious 
  experimental 
  difficulties 
  were 
  encountered 
  with 
  

   stannic 
  chloride 
  and 
  carbon 
  tetrachloride, 
  owing 
  to 
  the 
  

   actiou 
  of 
  these 
  substances 
  on 
  mercury, 
  stannic 
  chloride 
  

   under 
  all 
  condition- 
  and 
  carbon 
  tetrachloride 
  at 
  the 
  higher 
  

   temperatures. 
  In 
  both 
  cases 
  it 
  was 
  necessary 
  to 
  devise 
  

   special 
  methods 
  Eor 
  the 
  determination 
  of 
  the 
  vapour 
  pres- 
  

   sures 
  and 
  specific 
  volumes, 
  and 
  it 
  is 
  not 
  to 
  be 
  expected 
  that 
  

   the 
  data 
  lor 
  these 
  substances 
  can 
  be 
  so 
  accurate 
  as 
  lor 
  the 
  

  

  ^/nl've 
  pointed 
  out 
  (Phil. 
  Mag. 
  vol. 
  1. 
  p. 
  291 
  (1900) 
  ) 
  that 
  

   although 
  the 
  law 
  of 
  Cailletet 
  and 
  Mathias 
  is 
  applicable 
  to 
  

  

  