﻿the 
  

   LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  [SIXTH 
  SERIES.] 
  

  

  AUGUST 
  1908. 
  

  

  XVI. 
  On 
  Orthobaric 
  Volumes 
  in 
  relation 
  to 
  Pressure 
  and 
  

   Temperature. 
  By 
  Edward 
  Haigh, 
  M.A., 
  B.Sc, 
  Senior 
  

   Master 
  at 
  Monkton 
  Combe 
  School, 
  near 
  Bath 
  

   [Plates 
  VI. 
  & 
  VII.] 
  

  

  Introduction. 
  

  

  MANY 
  years 
  ago, 
  in 
  connexion 
  with 
  an 
  attempt 
  to 
  obtain 
  

   a 
  corrected 
  form 
  of 
  van 
  der 
  Waals's 
  equation, 
  the 
  

   writer 
  commenced 
  a 
  detailed 
  study 
  o£ 
  the 
  particular 
  case 
  in 
  

   which 
  a 
  liquid 
  is 
  in 
  equilibrium 
  with 
  its 
  saturated 
  vapour. 
  

   It 
  is 
  evident 
  from 
  the 
  numerous 
  theorems 
  which 
  have 
  been 
  

   formulated 
  relating 
  to 
  " 
  corresponding 
  states," 
  that 
  those 
  

   properties 
  of 
  a 
  substance 
  which 
  depend 
  upon 
  the 
  relations 
  of 
  

   pressure, 
  temperature, 
  and 
  volume 
  are 
  intimately 
  connected 
  

   with 
  the 
  values 
  of 
  the 
  three 
  critical 
  constants. 
  Reduced 
  data 
  

   have 
  accordingly 
  been 
  employed 
  almost 
  exclusively 
  in 
  this 
  

   paper, 
  the 
  primary 
  aim 
  of 
  the 
  investigation 
  being 
  to 
  ascertain 
  

   whether 
  any 
  equation 
  could 
  be 
  found 
  connecting 
  pressure, 
  

   temperature, 
  and 
  volume 
  without 
  the 
  employment 
  of 
  any 
  

   other 
  constants 
  than 
  simple 
  functions 
  of 
  the 
  critical 
  values 
  of 
  

   these 
  variables. 
  The 
  problem 
  has 
  long 
  baffled 
  solution, 
  but 
  

   recently 
  it 
  has 
  been 
  found 
  possible 
  to 
  formulate 
  an 
  equation 
  

   of 
  the 
  desired 
  type 
  which 
  is 
  in 
  substantial 
  agreement 
  with 
  

   the 
  results 
  of 
  experiment. 
  On 
  a 
  pressure-volume 
  diagram, 
  

   the 
  equation 
  connects 
  the 
  coordinates 
  of 
  two 
  isobaric 
  points 
  

   on 
  each 
  isothermal 
  below 
  the 
  critical 
  point. 
  Since 
  no 
  

   attempt 
  has 
  been 
  made 
  to 
  take 
  account 
  of 
  the 
  anomalies 
  due 
  

   directly 
  to 
  polymerization, 
  the 
  equations 
  given 
  below 
  have 
  

  

  * 
  Communicated 
  by 
  Professor 
  Young, 
  F.R.S. 
  

   Phil. 
  Mag. 
  S. 
  0. 
  Vol. 
  1G. 
  No. 
  92. 
  Aug. 
  1908. 
  P 
  

  

  