Fluid EoS #27 ("C-O-H hybrid") permits calculations with unbuffered C-O-H fluid. The primary 
reason for using this EoS is to model processes in which graphite or diamond may be dissolved 
or precipiated in response to devolatilization (i.e., including redox) processes. 

To use this EoS:

1) The thermodynamic data file must specify components that span the C-O-H composition space, 
   e.g., H2, O2, and C. Thermodynamic data files with components such as H2O and CO2 can be 
   transformed to files with appropriate components (e.g., CO2->C, H2O->H2) using the program 
   CTRANSF.

2) To avoid confusing prompts from BUILD, the thermodynamic data file should not specify special 
   components, i.e., if the header section of the thermodynamic file contains a section marked
   off by the begin_special_components/end_special_components keywords, e.g.,

   begin_special_components
   H2
   O2
   end_special_components         
                         
   the section should be deleted.

3) The EoS tags for H2 and O2 in thermodynamic data file must be set to, respectively, 105 and 
   107, as in:

   H2       EoS = 105
   H2(1)
   G0 = -38968.2 S0 = 130.7  
   c1 = 23.3 c2 = .4627E-2 c5 = 76.3   
   end

   O2       EoS = 107 
   O2(1)
   G0 = -61180.38 S0 = 205.2  
   c1 = 48.3 c2 = -.691E-3 c3 = 499200 c5 = -420.7  
   end

4) When running BUILD:
   a) specify H2, O2, and C as thermodynamic components. 
   b) exclude all C-O-H fluid species other than H2 and O2 (e.g., CO, CO2, H2O, h2oL) and, if 
      present, any O2 or H2 buffers (e.g., qfm, mthm).  
   c) answer yes to prompt asking whether the calculation should include solution models. 
      Specify the solution model file "solution_model.dat". Select the solution model "COHF" 
      and any other solution models of interest.

5) Some thermodynamic data files (e.g., hp11ver_metal.dat or metal_mix.dat) contain data from 
   different sources for graphite and diamond (e.g., gph, gphb, GPH, diam, diamb, and DIAM). Make 
   sure that carbon endmember of the COHF solution model in solution_model.dat corresponds to 
   the graphite data of the source that interests you, e.g., if you intend to use Brosh's data 
   (gphb and diamb), then the carbon endmember of the COHF solution model must be "gphb".