In Fortran, you will need to include the source file IPhreeqc_interface.F90
in your project files. This file defines the IPhreeqc Fortran module. This
is the preferred method to use IPhreeqc from a Fortran program.

     USE IPhreeqc
     INTEGER(KIND=4) id
     id = CreateIPhreeqc()

Use of the include files IPhreeqc.f.inc and IPhreeqc.f90.inc has been
deprecated. To continue using them you must unset IPHREEQC_ENABLE_MODULE in
CMake builds or use the --disable-fortran-module in configure builds. If 
either of these settings are used the Fortran include files will be
installed to the include directory.

     INCLUDE 'IPhreeqc.f90.inc'
     INTEGER(KIND=4) id
     id = CreateIPhreeqc()