﻿Vapour- 
  Pressures 
  of 
  Carbon 
  Dioxide. 
  155 
  

  

  Table 
  II. 
  

   Vapour-Pressures 
  of 
  Carbon 
  Dioxide 
  (read 
  from 
  curve) 
  . 
  

  

  Temperature. 
  

  

  Pressure. 
  

  

  

  

  Atmospheres. 
  

  

  Metres 
  of 
  Mercury. 
  

  

  343 
  

  

  261 
  

  

  - 
  5 
  

  

  30-0 
  

  

  22-8 
  

  

  -10 
  

  

  260 
  

  

  198 
  

  

  -15 
  

  

  224 
  

  

  170 
  

  

  -20 
  

  

  193 
  

  

  14-7 
  

  

  -25 
  

  

  165 
  

  

  12-5 
  

  

  -30 
  

  

  14-0 
  

  

  106 
  

  

  -35 
  

  

  11-8 
  

  

  8-97 
  

  

  -40 
  

   -45 
  

  

  9-82 
  

  

  746 
  

   6-17 
  | 
  

  

  

  8-12 
  

  

  

  

  -50 
  

  

  6-60 
  

  

  Solid. 
  

  

  5-02 
  Solid. 
  

  

  -55 
  

   -60 
  

  

  5-35 
  

   430 
  

  

  

  407 
  

   3-27 
  

  

  

  3-97 
  

  

  302 
  

  

  -65 
  

  

  

  2-77 
  

  

  

  211 
  

  

  -70 
  

  

  

  1-88 
  

  

  

  1-43 
  | 
  

  

  -75 
  

  

  

  1-28 
  

  

  

  •97 
  

  

  -78-32 
  

  

  

  1-00 
  

  

  

  •76 
  ! 
  

  

  On 
  close 
  inspection 
  Table 
  I. 
  shows 
  certain 
  small 
  irregu- 
  

   larities; 
  the 
  reading 
  marked 
  by 
  an 
  asterisk 
  does 
  not 
  get 
  

   into 
  the 
  curve 
  and 
  must 
  be 
  affected 
  by 
  a 
  small 
  error 
  of 
  

   observation. 
  The 
  remaining 
  irregularities 
  are 
  very 
  small, 
  

   and 
  may 
  be 
  accounted 
  for 
  by 
  the 
  various 
  uncertainties 
  of 
  the 
  

   method 
  : 
  they 
  do 
  not, 
  however, 
  affect 
  the 
  first 
  decimal 
  of 
  the 
  

   values 
  of 
  the 
  vapour-pressures. 
  In 
  addition 
  to 
  the 
  accidental 
  

   errors 
  there 
  is 
  the 
  systematic 
  error 
  due 
  to 
  the 
  impurity 
  of 
  

   the 
  gas. 
  In 
  the 
  case 
  of 
  carbon 
  dioxide 
  this 
  impurity 
  was 
  

   very 
  small 
  : 
  after 
  a 
  change 
  of 
  temperature 
  the 
  pressure 
  

   adjusted 
  itself 
  almost 
  immediately 
  to 
  its 
  final 
  value, 
  and 
  a 
  

   change 
  of 
  volume 
  had 
  a 
  very 
  slight 
  effect 
  on 
  the 
  pressure. 
  

   At 
  C. 
  the 
  pressure 
  at 
  a 
  large 
  volume 
  with 
  only 
  a 
  little 
  

   liquid 
  carbon 
  dioxide 
  present 
  was 
  34*32 
  ; 
  and 
  at 
  a 
  small 
  

   volume, 
  with 
  most 
  of 
  the 
  gas 
  liquefied, 
  the 
  pressure 
  was 
  34'3# 
  

   atmos 
  

  

  Because 
  of 
  the 
  scarcity 
  of 
  diagrams 
  of 
  the 
  kind, 
  we 
  think 
  

   it 
  may 
  be 
  of 
  interest 
  to 
  publish 
  the 
  triple-point 
  diagram 
  for 
  

   carbon 
  dioxide. 
  It 
  will 
  be 
  seen 
  that 
  the 
  liquid 
  may 
  be 
  con- 
  

   siderably 
  undercooled, 
  the 
  lowest 
  liquid-vapour 
  point 
  being 
  

   seven 
  degrees 
  below 
  the 
  triple-point. 
  The 
  triple-point 
  was 
  

   determined 
  directly 
  by 
  changing 
  the 
  temperature 
  until 
  no 
  

   gradual 
  change 
  in 
  the 
  amount 
  of 
  solid 
  was 
  observable, 
  and, 
  

   indirectly, 
  by 
  finding 
  the 
  point 
  of 
  intersection 
  of 
  the 
  solid- 
  

  

  