def Region2_cp0(Tr, Pr):
    """Ideal properties for Region 2

    Parameters
    ----------
    Tr : float
        Reduced temperature, [-]
    Pr : float
        Reduced pressure, [-]

    Returns
    -------
    prop : array
        Array with ideal Gibbs energy partial derivatives:

            * g: Ideal Specific Gibbs energy [kJ/kg]
            * gp: ∂g/∂P|T
            * gpp: ∂²g/∂P²|T
            * gt: ∂g/∂T|P
            * gtt: ∂²g/∂T²|P
            * gpt: ∂²g/∂T∂P

    References
    ----------
    IAPWS, Revised Release on the IAPWS Industrial Formulation 1997 for the
    Thermodynamic Properties of Water and Steam August 2007,
    http://www.iapws.org/relguide/IF97-Rev.html, Eq 16

    """
    Jo = [0, 1, -5, -4, -3, -2, -1, 2, 3]
    no = [-0.96927686500217E+01, 0.10086655968018E+02, -0.56087911283020E-02,
          0.71452738081455E-01, -0.40710498223928E+00, 0.14240819171444E+01,
          -0.43839511319450E+01, -0.28408632460772E+00, 0.21268463753307E-01]
    go = log(Pr)
    gop = Pr**-1
    gopp = -Pr**-2
    got = gott = gopt = 0
    for j, ni in zip(Jo, no):
        go += ni * Tr**j
        got += ni*j * Tr**(j-1)
        gott += ni*j*(j-1) * Tr**(j-2)
    return go, gop, gopp, got, gott, gopt