﻿164 
  

  

  Prof. 
  W. 
  A. 
  Pouglas 
  Rudge 
  

  

  on 
  

  

  about 
  21° 
  C, 
  and 
  under 
  a 
  difference 
  o£ 
  pressure 
  of 
  57 
  

   atmospheres. 
  

  

  A 
  second 
  series 
  o£ 
  experiments 
  was 
  undertaken 
  in 
  which 
  

   the 
  gas 
  was 
  heated 
  to 
  a 
  point 
  above 
  its 
  critical 
  temperature,, 
  

   so 
  that 
  the 
  latent 
  heat 
  o£ 
  evaporation 
  did 
  not 
  require 
  con- 
  

   sideration. 
  The 
  same 
  apparatus 
  was 
  used, 
  the 
  necessary 
  

   temperature 
  being 
  reached 
  by 
  sending 
  an 
  electric 
  current 
  

   through 
  the 
  coil. 
  The 
  usual 
  temperature 
  was 
  from 
  36° 
  C. 
  

   to 
  40° 
  C 
  The 
  experiment 
  was 
  carried 
  out 
  as 
  follows 
  : 
  — 
  A 
  

   constant 
  current 
  measured 
  by 
  a 
  Siemerr's 
  milliampere 
  metre 
  

   provided 
  with 
  shunts, 
  was 
  sent 
  through 
  the 
  manganin 
  coil, 
  a 
  

   carbon 
  rheostat 
  being 
  included 
  in 
  the 
  circuit 
  so 
  as 
  to 
  keep 
  

   the 
  current 
  at 
  a 
  steady 
  value, 
  and 
  this 
  could 
  be 
  done 
  to 
  about 
  

   0'5 
  per 
  cent. 
  Observations 
  were 
  taken 
  of 
  time 
  and 
  tempe-- 
  

   rature 
  from 
  about 
  32° 
  to 
  40° 
  and 
  curves 
  plotted 
  : 
  

  

  (1) 
  When 
  the 
  calorimeter 
  containing 
  the 
  bulb 
  was 
  heated 
  

   and 
  the 
  gas 
  not 
  allowed 
  to 
  escape 
  ; 
  

  

  (2) 
  When 
  the 
  gas 
  escaped 
  during 
  the 
  heating. 
  

  

  The 
  rate 
  of 
  rise 
  in 
  temperature 
  was 
  greater 
  in 
  (1) 
  than 
  

   in 
  (2), 
  and 
  by 
  comparison 
  of 
  the 
  curves 
  the 
  fall 
  in 
  tempera- 
  

   ture 
  during 
  the 
  escape 
  of 
  the 
  gas 
  was 
  found. 
  

  

  The 
  following 
  table 
  gives 
  the 
  result 
  of 
  one 
  experiment. 
  

  

  Table 
  II. 
  

  

  (1) 
  

  

  (2) 
  

  

  When 
  the 
  gas 
  not 
  allowed 
  

  

  During 
  the 
  escape 
  of 
  

  

  to 
  escape. 
  

  

  the 
  gas. 
  

  

  Thne. 
  

  

  1 
  

   Temperature. 
  

  

  Time. 
  

  

  Temperature. 
  

  

  

  

  31-15 
  

  

  18 
  

  

  31-3 
  

  

  2 
  

  

  33-1 
  

  

  20 
  

  

  3305 
  

  

  4 
  

  

  34-8 
  

  

  *G. 
  22 
  

  

  34-75 
  

  

  6 
  

  

  36-4 
  

  

  23 
  

  

  35-35 
  

  

  8 
  

  

  38-0 
  

  

  24 
  

  

  35-95 
  

  

  10 
  

  

  39-5 
  

  

  25 
  

  

  36-7 
  

  

  12 
  

  

  41-0 
  

  

  26 
  

  

  37-3 
  

  

  14 
  

  

  42-4 
  

  

  27 
  

  

  37-9 
  

  

  16 
  

  

  43-8 
  

  

  28 
  

  

  38-5 
  

  

  

  

  29 
  

  

  39-15 
  

  

  

  

  30 
  

  

  39-85 
  

  

  

  

  32 
  

  

  41-2 
  

  

  

  

  34 
  

  

  42-6 
  

  

  

  

  36 
  

  

  43 
  

  

  * 
  Gr 
  indicates 
  when 
  the 
  gas 
  is 
  liberated. 
  

  

  These 
  two 
  curves 
  (fig. 
  2) 
  become 
  parallel 
  after 
  the 
  evolution 
  

   of 
  gas 
  has 
  ceased, 
  and 
  the 
  difference 
  between 
  two 
  points 
  on 
  

  

  