﻿192 
  

  

  Allen 
  and 
  Lombard 
  — 
  Determination 
  of 
  

  

  tial 
  pressure 
  of 
  sulphur 
  in 
  hydrogen 
  sulphide 
  at 
  this 
  temperature 
  

   was 
  estimated 
  to 
  be 
  about 
  5 
  mm 
  . 
  The 
  free 
  hydrogen 
  very 
  likely 
  

   has 
  an 
  influence 
  on 
  this 
  equilibrium, 
  for 
  in 
  pure 
  sulphur 
  vapor 
  

   we 
  now 
  find 
  the 
  dissociation 
  pressure 
  of 
  pyrite 
  to 
  be 
  less 
  than 
  

   l 
  mm 
  at 
  the 
  above 
  temperature. 
  In 
  the 
  same 
  investigation 
  a 
  

   strong 
  absorption 
  of 
  heat 
  was 
  found 
  in 
  pyrite 
  between 
  665° 
  

  

  Fig. 
  6. 
  

  

  600 
  

  

  500 
  

  

  Si 
  

  

  O 
  

  

  CO 
  

   Si 
  

   Pi 
  

  

  co 
  

  

  03 
  

   <D 
  

   Si 
  

  

  400 
  

  

  300 
  

  

  200 
  

  

  100 
  

  

  _ 
  

  

  

  575 
  

  

  595 
  

  

  615 
  635 
  

  

  Temperature 
  — 
  C° 
  . 
  

  

  655 
  

  

  675 
  

  

  695 
  

  

  Fig. 
  6. 
  Dissociation 
  pressure 
  curve 
  of 
  pyrite 
  (FeS 
  2 
  ). 
  

  

  and 
  685° 
  which 
  was 
  attributed 
  to 
  the 
  fact 
  that 
  the 
  sulphur 
  

   pressure 
  had 
  reached 
  1 
  atmosphere. 
  This 
  is 
  confirmed 
  by 
  the 
  

   present 
  work. 
  A 
  short 
  extrapolation 
  of 
  the 
  curve 
  plotted 
  in 
  

   fig. 
  6 
  indicates 
  that 
  a 
  pressure 
  of 
  76 
  cm 
  would 
  be 
  reached 
  about 
  

   689°. 
  One 
  atmosphere 
  pressure 
  is 
  evidently 
  reached 
  only 
  at 
  

   the 
  itpjyer 
  end 
  of 
  this 
  absorption 
  interval 
  (665° 
  -685°) 
  rather 
  

   than 
  the 
  lower 
  as 
  we 
  then 
  supposed. 
  

  

  