﻿THE 
  

  

  AMERICAN 
  JOURNALOFSCIENCE 
  

  

  [FOURTH 
  SERIES.] 
  

  

  Art. 
  XVII. 
  — 
  A 
  Method 
  for 
  the 
  Determination 
  of 
  Dis- 
  

   sociation 
  Pressures 
  of 
  Sulphides* 
  and 
  its 
  Application 
  to 
  

   Covel 
  lite 
  (OuS) 
  and 
  Pyrite 
  (Pe$ 
  2 
  ) 
  ; 
  by 
  E. 
  T. 
  Allen 
  and 
  

   Robert 
  H. 
  Lombard. 
  

  

  I. 
  Introduction. 
  

  

  Among 
  the 
  sulphides 
  there 
  are 
  a 
  considerable 
  number, 
  if 
  we 
  

   include 
  those 
  of 
  complex 
  composition, 
  which 
  dissociate 
  (lose 
  

   sulphur) 
  at 
  accessible 
  temperatures. 
  In 
  all 
  such 
  instances 
  the 
  

   dissociation 
  pressure 
  is 
  of 
  course 
  an 
  essential 
  condition 
  of 
  

   formation 
  of 
  the 
  sulphide. 
  This 
  fact 
  was 
  impressed 
  upon 
  us 
  

   in 
  a 
  preliminary 
  study 
  f 
  of 
  the 
  sulphides 
  of 
  iron 
  and 
  copper. 
  

   Very 
  little 
  work 
  has 
  been 
  done 
  on 
  the 
  subject; 
  in 
  fact 
  only 
  the 
  

   dissociation 
  pressure 
  of 
  covellite 
  (cupric 
  sulphide) 
  seems 
  to 
  

   have 
  been 
  studied 
  with 
  any 
  approach 
  to 
  accuracy, 
  though 
  

   some 
  preliminary 
  work 
  has 
  been 
  attempted 
  with 
  pyrite.J 
  In 
  

   measuring 
  the 
  pressures 
  of 
  sulphur 
  vapor, 
  it 
  is 
  obvious 
  that 
  a 
  

   mercury 
  gauge 
  would 
  be 
  out 
  of 
  the 
  question. 
  Three§ 
  methods 
  

   have 
  been 
  employed 
  heretofore 
  ; 
  a 
  dynamic 
  method 
  in 
  which 
  

   is 
  determined 
  the 
  quantity 
  of 
  sulphur 
  volatilized 
  in 
  a 
  measured 
  

  

  * 
  This 
  work 
  is 
  a 
  portion 
  of 
  an 
  investigation 
  of 
  the 
  copper 
  sulphide-ores 
  

   undertaken 
  by 
  this 
  laboratory 
  in 
  co-operation 
  with 
  Prof. 
  L. 
  C. 
  Graton 
  and 
  

   colleagues 
  of 
  the 
  Harvard 
  Mining 
  School. 
  

  

  f 
  Annual 
  Eeport 
  of 
  the 
  Director 
  of 
  the 
  Geophysical 
  Laboratory, 
  1914, 
  

   p. 
  156. 
  

  

  ^Karl 
  Schubert, 
  Dissociation 
  der 
  einiger 
  Oxyde, 
  Karbonate, 
  und 
  Sul- 
  

   phide. 
  Dissertation, 
  Berlin, 
  1909. 
  Schubert 
  made 
  use 
  of 
  the 
  Victor 
  Meyer 
  

   principle. 
  See 
  also 
  Hempel 
  and 
  Schubert, 
  Z. 
  fur 
  Elektrocheniie, 
  xviii, 
  729, 
  

   1912. 
  

  

  § 
  A 
  method 
  for 
  the 
  determination 
  of 
  vapor 
  densities 
  at 
  high 
  temperatures 
  

   published 
  by 
  G. 
  E. 
  Gibson 
  might 
  be 
  used 
  for 
  the 
  solution 
  of 
  this 
  problem. 
  

   The 
  method 
  depends 
  on 
  the 
  elasticity 
  of 
  a 
  quartz 
  membrane. 
  Unfortunately 
  

   the 
  apparatus 
  appears 
  to 
  be 
  unusually 
  difficult 
  to 
  construct. 
  See 
  G. 
  E. 
  Gib- 
  

   son, 
  Dissertation, 
  Breslau, 
  1911 
  ; 
  also 
  Proc. 
  Eoy. 
  Soc. 
  Edinburgh, 
  xxxiii, 
  1, 
  

   1912. 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  XLIII, 
  No. 
  255.— 
  March, 
  1917. 
  

   13 
  

  

  