subroutine TRNPRP (t,rho,x,eta,tcx,ierr,herr)
c
c  compute the transport properties of thermal conductivity and
c  viscosity as functions of temperature, density, and composition
c
c  inputs:
c        t--temperature (K)
c      rho--molar density (mol/L)
c        x--composition array (mol frac)
c  outputs:
c      eta--viscosity (uPa.s)
c      tcx--thermal conductivity (W/m.K)
c     ierr--error flag:  0 = successful
c                      -31 = temperature out of range for conductivity
c                      -32 = density out of range for conductivity
c                      -33 = T and D out of range for conductivity
c                      -41 = temperature out of range for viscosity
c                      -42 = density out of range for viscosity
c                      -43 = T and D out of range for viscosity
c                      -51 = T out of range for both visc and t.c.
c                      -52 = D out of range for both visc and t.c.
c                      -53 = T and/or D out of range for visc and t.c.
c                       39 = model not found for thermal conductivity
c                       49 = model not found for viscosity
c                       50 = ammonia/water mix (no properties calculated)
c                       51 = exactly at t_crit, rho_crit for a pure
c                            fluid; tcx is infinite
c                  -58,-59 = ECS model did not converge
c     herr--error string (character*255 variable if ierr<>0)


MISCELLANEOUS PROPERTIES

The following routines return the dielectric constant, melting line, and
sublimation line.  These properties are not available for all fluids in
REFPROP.


      subroutine DIELEC (t,rho,x,de)
c
c  compute the dielectric constant as a function of temperature, density,
c  and composition.
c
c  inputs:
c        t--temperature [K]
c      rho--molar density [mol/L]
c        x--composition [array of mol frac]
c   output:
c       de--dielectric constant


      subroutine MELTT (t,x,p,ierr,herr)
c
c  compute the melting line pressure as a function of temperature
c  and composition.
c
c  inputs:
c        t--temperature [K]
c        x--composition [array of mol frac]
c   output:
c        p--melting line pressure [kPa]
c        ierr--error flag:  0 = successful
c        herr--error string (character*255 variable if ierr<>0)


      subroutine MELTP (p,x,t,ierr,herr)
c
c  compute the melting line temperature as a function of pressure
c  and composition.
c
c  inputs:
c        p--melting line pressure [kPa]
c        x--composition [array of mol frac]
c   output:
c        t--temperature [K]
c        ierr--error flag:  0 = successful
c        herr--error string (character*255 variable if ierr<>0)

      subroutine SUBLT (t,x,p,ierr,herr)
c
c  compute the sublimation line pressure as a function of temperature
c  and composition.
c
c  inputs:
c        t--temperature [K]
c        x--composition [array of mol frac]
c   output:
c        p--sublimation line pressure [kPa]
c        ierr--error flag:  0 = successful
c        herr--error string (character*255 variable if ierr<>0)



      subroutine SUBLP (p,x,t,ierr,herr)
c
c  compute the sublimation line temperature as a function of pressure
c  and composition.
c
c  inputs:
c        p--sublimation line pressure [kPa]
c        x--composition [array of mol frac]
c   output:
c        t--temperature [K]
c        ierr--error flag:  0 = successful
c        herr--error string (character*255 variable if ierr<>0)


UTILITY SUBROUTINES

The following "utility" routines provide fluid constants, such as the
molecular weight, and provide conversions between mass and molar
quantities.

      subroutine INFO (icomp,wm,ttp,tnbp,tc,pc,Dc,Zc,acf,dip,Rgas)
c
c  provides fluid constants for specified component
c
c  input:
c    icomp--component number in mixture; 1 for pure fluid
c  outputs:
c       wm--molecular weight [g/mol]
c      ttp--triple point temperature [K]
c     tnbp--normal boiling point temperature [K]
c       tc--critical temperature [K]
c       pc--critical pressure [kPa]
c       Dc--critical density [mol/L]
c       Zc--compressibility at critical point [pc/(Rgas*Tc*Dc)]
c      acf--accentric factor [-]
c      dip--dipole moment [debye]
c     Rgas--gas constant [J/mol-K]



      subroutine NAME (icomp,hname,hn80,hcas)
c
c  provides name information for specified component
c
c  input:
c    icomp--component number in mixture; 1 for pure fluid
c  outputs:
c    hname--component name [character*12]
c     hn80--component name--long form [character*80]
c     hcas--CAS (Chemical Abstracts Service) number [character*12]



      function WMOL (x)
c
c  molecular weight for a mixture of specified composition
c
c  input:
c        x--composition array [array of mol frac]
c
c  output (as function value):
c     WMOL--molar mass [g/mol], a.k.a. "molecular weight"



      subroutine XMASS (xmol,xkg,wmix)
c
c  converts composition on a mole fraction basis to mass fraction
c
c  input:
c     xmol--composition array [array of mol frac]
c  outputs:
c      xkg--composition array [array of mass frac]
c     wmix--molar mass of the mixture [g/mol], a.k.a. "molecular weight"



      subroutine XMOLE (xkg,xmol,wmix)
c
c  converts composition on a mass fraction basis to mole fraction
c
c  input:
c      xkg--composition array [array of mass frac]
c  outputs:
c     xmol--composition array [array of mol frac]
c     wmix--molar mass of the mixture [g/mol], a.k.a. "molecular weight"



      subroutine QMOLE (qkg,xlkg,xvkg,qmol,xl,xv,wliq,wvap,ierr,herr)
c
c  converts quality and composition on a mass basis to a molar basis
c
c  inputs:
c      qkg--quality on mass basis [mass of vapor/total mass]
c           qkg = 0 indicates saturated liquid
c           qkg = 1 indicates saturated vapor
c           0 < qkg < 1 indicates a two-phase state
c           qkg < 0 or qkg > 1 are not allowed and will result in warning
c     xlkg--mass composition of liquid phase [array of mass frac]
c     xvkg--mass composition of vapor phase [array of mass frac]
c  outputs:
c     qmol--quality on mass basis [mass of vapor/total mass]
c       xl--molar composition of liquid phase [array of mol frac]
c       xv--molar composition of vapor phase [array of mol frac]
c     wliq--molecular weight of liquid phase [g/mol]
c     wvap--molecular weight of vapor phase [g/mol]
c     ierr--error flag:  0 = all inputs within limits
c           -19:  input q < 0 or > 1
c     herr--error string (character*255 variable if ierr<>0)



      subroutine QMASS (qmol,xl,xv,qkg,xlkg,xvkg,wliq,wvap,ierr,herr)
c
c  converts quality and composition on a mole basis to a mass basis
c
c  inputs:
c     qmol--molar quality [moles vapor/total moles]
c           qmol = 0 indicates saturated liquid
c           qmol = 1 indicates saturated vapor
c           0 < qmol < 1 indicates a two-phase state
c           qmol < 0 or qmol > 1 are not allowed and will result in warning
c       xl--composition of liquid phase [array of mol frac]
c       xv--composition of vapor phase [array of mol frac]
c  outputs:
c      qkg--quality on mass basis [mass of vapor/total mass]
c     xlkg--mass composition of liquid phase [array of mass frac]
c     xvkg--mass composition of vapor phase [array of mass frac]
c     wliq--molecular weight of liquid phase [g/mol]
c     wvap--molecular weight of vapor phase [g/mol]
c     ierr--error flag:  0 = all inputs within limits
c           -19:  input q < 0 or > 1
c     herr--error string (character*255 variable if ierr<>0)

      subroutine LIMITX (htyp,t,D,p,x,tmin,tmax,Dmax,pmax,ierr,herr)
c
c  returns limits of a property model as a function of composition
c  and/or checks input t, D, p against those limits
c
c  Pure fluid limits are read in from the .fld files; for mixtures, a
c  simple mole fraction weighting in reduced variables is used.
c
c  Attempting calculations below the mininum temperature and/or above
c  the maximum density will result in an error.  These will often
c  correspond to a physically unreasonable state; also many equations of
c  state do not extrapolate reliably to lower T's and higher D's.
c
c  A warning is issued if the temperature is above the maximum but below
c  1.5 times the maximum; similarly pressures up to twice the maximum
c  result in only a warning. Most equations of state may be
c  extrapolated to higher T's and P's.  Temperatures and/or pressures
c  outside these extended limits will result in an error.
c
c  When temperature is unknown, set t to -1 to avoid performing
c  the melting line check
c
c  inputs:
c     htyp--flag indicating which models are to be checked [character*3]
c           'EOS':  equation of state for thermodynamic properties
c           'ETA':  viscosity
c           'TCX':  thermal conductivity
c           'STN':  surface tension
c        t--temperature [K]
c        D--molar density [mol/L]
c        p--pressure [kPa]
c        x--composition array [mol frac]
c     N.B.--all inputs must be specified, if one or more are not
c           available, (or not applicable as in case of surface tension)
c           use reasonable values, such as:
c           t = tnbp
c           D = 0
c           p = 0
c  outputs:
c     tmin--minimum temperature for model specified by htyp [K]
c     tmax--maximum temperature [K]
c     Dmax--maximum density [mol/L]
c     pmax--maximum pressure [kPa]

c     ierr--error flag:  0 = all inputs within limits
c                      <>0 = one or more inputs outside limits:
c                       -1 = 1.5*tmax > t > tmax
c                        1 = t < tmin or t > 1.5*tmax
c                        2 = D > Dmax or D < 0
c                       -4 = 2*pmax > p > pmax
c                        4 = p < 0 or p > 2*pmax
c                        8 = component composition < 0 or > 1
c                            and/or composition sum < 0 or > 1
c                       16 = p>pmelt
c                      -16 = t<ttrp (important for water)
c           if multiple inputs are outside limits, ierr = abs[sum(ierr)]
c           with the sign determined by the most severe excursion
c           (ierr > 0 indicate an error--calculations not possible,
c            ierr < 0 indicate a warning--results may be questionable)
c     herr--error string (character*255 variable if ierr<>0)



      subroutine LIMITK (htyp,icomp,t,D,p,tmin,tmax,Dmax,pmax,ierr,herr)
c
c  returns limits of a property model (read in from the .fld files) for
c  a mixture component and/or checks input t, D, p against those limits
c
c  This routine functions in the same manner as LIMITX except that the
c  composition x is replaced by the component number icomp.
c
c  See the description of LIMITX for input and output information.




      subroutine ERRMSG (ierr,herr)
c
c  write error messages to default output; this subroutine should be
c  called immediately after any call to a subroutine which potentially
c  can error out
c
c  inputs:
c     ierr--error flag:  0 = successful (no message will be written)
c                       <0 = warning
c                       >0 = error
c     herr--error string (character*255 variable)
c
c  outputs:
c     none--error string written to default output
c
c     N.B.  the statement which writes output to the screen is
c           commented out to avoid problems with the DLL; this must be
c           uncommented if you wish to see error messages on the screen;
c           alternately, open a file from within your application and
c           replace the "write (*,1000)" with "write (unit=i,1000)" to
c           write the messages to that file (where i is a logical unit)