﻿Dissociation 
  Pressures 
  of 
  Sulphides. 
  

  

  177 
  

  

  This 
  method 
  suggested 
  itself 
  to 
  us 
  during 
  a 
  study 
  of 
  the 
  

   copper-iron 
  sulphides. 
  At 
  that 
  time 
  we 
  were 
  unaware 
  of 
  the 
  

   fact 
  that 
  Wasjuchnowa 
  had 
  made 
  use 
  of 
  the 
  same 
  principle, 
  

   though 
  less 
  conveniently 
  applied, 
  in 
  a 
  control 
  method, 
  the 
  

   second 
  mentioned 
  above. 
  She 
  even 
  conceived 
  the 
  idea 
  of 
  

   using 
  an 
  evacuated 
  tube, 
  though 
  she 
  never 
  actually 
  tried 
  it. 
  

   The 
  method 
  was 
  used 
  by 
  her 
  as 
  a 
  control 
  only, 
  most 
  of 
  her 
  

   work 
  having 
  been 
  done 
  by 
  the 
  dynamic 
  method. 
  

  

  Apparatus. 
  — 
  The 
  tube 
  used 
  in 
  our 
  measurements 
  (see 
  fig. 
  1) 
  

   is 
  made 
  of 
  Jena 
  combustion 
  glass 
  where 
  temperatures 
  below 
  

   about 
  675° 
  are 
  to 
  be 
  reached 
  ; 
  for 
  higher 
  temperatures 
  quartz- 
  

  

  FlG. 
  l. 
  

  

  Fig. 
  1. 
  Tube 
  of 
  glass 
  (or 
  quartz 
  glass) 
  for 
  the 
  determination 
  of 
  dis- 
  

   sociation 
  pressure. 
  1. 
  Side 
  view. 
  2. 
  Top 
  view. 
  

  

  glass 
  is 
  employed. 
  The 
  apparatus 
  is 
  constructed 
  as 
  follows 
  : 
  

   Two 
  glass 
  tubes, 
  about 
  l 
  cm 
  in 
  inside 
  diameter, 
  are 
  first 
  sealed 
  

   to 
  either 
  end 
  of 
  a 
  stem 
  of 
  proper 
  length 
  and 
  about 
  5 
  mm 
  in 
  

   inside 
  diameter. 
  One 
  of 
  the 
  tubes 
  is 
  then 
  closed 
  and 
  blown 
  

   into 
  a 
  small 
  cylindrical 
  bulb 
  about 
  2 
  cm 
  in 
  length 
  to 
  hold 
  the 
  

   sulphur. 
  To 
  prevent 
  the 
  liquid 
  sulphur 
  from 
  flowing 
  out 
  into 
  

   the 
  stem, 
  the 
  bend 
  at 
  B 
  is 
  made. 
  Two 
  glass 
  hooks 
  to 
  hold 
  the 
  

   thermocouples 
  in 
  place 
  are 
  now 
  attached 
  at 
  E 
  } 
  and 
  E 
  2 
  . 
  A 
  con- 
  

   striction 
  D 
  is 
  then 
  made 
  at 
  a 
  convenient 
  distance 
  from 
  the 
  

   open 
  end 
  of 
  the 
  tube 
  after 
  which 
  about 
  0'5 
  g.* 
  of 
  pure 
  sulphurf 
  

   is 
  dropped 
  into 
  the 
  bulb 
  A, 
  melted 
  and 
  solidified. 
  A 
  small 
  

   glass 
  tube 
  which 
  contains 
  0*2 
  g. 
  or 
  more 
  of 
  powdered 
  sulphide 
  

   is 
  now 
  slipped 
  into 
  the 
  bulb 
  C. 
  In 
  some 
  cases 
  small 
  lumps 
  

   about 
  2 
  mm 
  in 
  diameter 
  were 
  substituted 
  for 
  the 
  powder. 
  D 
  is 
  

  

  * 
  This 
  quantity 
  always 
  insures 
  a 
  liquid 
  phase 
  under 
  our 
  working 
  condi- 
  

   tions. 
  

  

  f 
  The 
  sulphur 
  we 
  used 
  was 
  three 
  times 
  distilled 
  in 
  vacuo. 
  Since 
  investiga- 
  

   tions 
  of 
  the 
  boiling 
  point 
  of 
  sulphur 
  have 
  disclosed 
  no 
  material 
  difference 
  in 
  

   the 
  boiling 
  points 
  of 
  different 
  samples, 
  and 
  since 
  our 
  results 
  make 
  no 
  pre- 
  

   tension 
  to 
  high 
  accuracy, 
  the 
  sulphur 
  used 
  in 
  these 
  experiments 
  was 
  not 
  

   further 
  investigated. 
  

  

  