﻿338 
  Fenner 
  — 
  Stability 
  Relations 
  of 
  Silica 
  Minerals. 
  

  

  form 
  is 
  less 
  than 
  that 
  of 
  an 
  unstable 
  form. 
  An 
  inversion-point 
  

   lies 
  at 
  the 
  intersection 
  of 
  two 
  vapor-pressure 
  curves. 
  These 
  

   same 
  relations 
  apply 
  to 
  the 
  functions 
  free 
  energy 
  and 
  thermo- 
  

  

  FlG. 
  1. 
  

  

  

  

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  q: 
  

  

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  > 
  

   o 
  o 
  > 
  

  

  TEMPERATURE 
  

  

  Fig. 
  1. 
  Stability 
  relations 
  of 
  the 
  silica 
  minerals. 
  

  

  dynamic 
  potential, 
  and, 
  as 
  absolute 
  values 
  are 
  unknown, 
  the 
  

   vapor-pressure 
  coordinate 
  could 
  as 
  well 
  be 
  considered 
  as 
  a 
  

   coordinate 
  of 
  free 
  energy 
  or 
  thermodynamic 
  potential. 
  

  

  