function [ n_data, tc, vir ] = secvir_values ( n_data )

%*****************************************************************************80
%
%% secvir_values() returns some values of the second virial coefficient.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    19 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Lester Haar, John Gallagher and George Kell,
%    NBS/NRC Steam Tables:
%    Thermodynamic and Transport Properties and Computer Programs
%      for Vapor and Liquid States of Water in SI Units,
%    Hemisphere Publishing Corporation, Washington, 1984,
%    TJ270.H3, pages 24-25.
%
%  Input:
%
%    integer N_DATA.  The user sets N_DATA to 0 before the first call.  
%    Thereafter, it should simply be the value returned by the previous call.
%
%  Output:
%
%    integer N_DATA.  On each call, the routine increments N_DATA by 1, and
%    returns the corresponding data; when there is no more data, the
%    output value of N_DATA will be 0 again.
%
%    real TC, the temperature, in degrees Celsius.
%
%    real VIR, the second virial coefficient, in
%    m^3/kg.
%
  n_max = 19;

  tc_vec = [ ...
        0.0E+00, ...
        5.0E+00, ...
       10.0E+00, ...
       20.0E+00, ...
       30.0E+00, ...
       40.0E+00, ...
       60.0E+00, ...
       90.0E+00, ...
      120.0E+00, ...
      150.0E+00, ...
      180.0E+00, ...
      210.0E+00, ...
      240.0E+00, ...
      300.0E+00, ...
      400.0E+00, ...
      500.0E+00, ...
      700.0E+00, ...
     1000.0E+00, ...
     2000.0E+00 ];

  vir_vec = [ ...
     -98.96E+00, ...
     -90.08E+00, ...
     -82.29E+00, ...
     -69.36E+00, ...
     -59.19E+00, ...
     -51.07E+00, ...
     -39.13E+00, ...
     -27.81E+00, ...
     -20.83E+00, ...
     -16.21E+00, ...
     -12.98E+00, ...
     -10.63E+00, ...
      -8.85E+00, ...
      -6.39E+00, ...
      -4.03E+00, ...
      -2.71E+00, ...
      -1.32E+00, ...
      -0.39E+00, ...
       0.53E+00 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

  if ( n_max < n_data )
    n_data = 0;
    tc = 0.0;
    vir = 0.0;
  else
    tc = tc_vec(n_data);
    vir = vir_vec(n_data);
  end

  return
end
