def _Dielectric(rho, T):
    """Equation for the Dielectric constant

    Parameters
    ----------
    rho : float
        Density, [kg/m³]
    T : float
        Temperature, [K]

    Returns
    -------
    epsilon : float
        Dielectric constant, [-]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * 238 ≤ T ≤ 1200

    Examples
    --------
    >>> _Dielectric(999.242866, 298.15)
    78.5907250
    >>> _Dielectric(26.0569558, 873.15)
    1.12620970

    References
    ----------
    IAPWS, Release on the Static Dielectric Constant of Ordinary Water
    Substance for Temperatures from 238 K to 873 K and Pressures up to 1000
    MPa, http://www.iapws.org/relguide/Dielec.html
    """
    # Check input parameters
    if T < 238 or T > 1200:
        raise NotImplementedError("Incoming out of bound")

    k = 1.380658e-23
    Na = 6.0221367e23
    alfa = 1.636e-40
    epsilon0 = 8.854187817e-12
    mu = 6.138e-30

    d = rho/rhoc
    Tr = Tc/T
    I = [1, 1, 1, 2, 3, 3, 4, 5, 6, 7, 10, None]
    J = [0.25, 1, 2.5, 1.5, 1.5, 2.5, 2, 2, 5, 0.5, 10, None]
    n = [0.978224486826, -0.957771379375, 0.237511794148, 0.714692244396,
         -0.298217036956, -0.108863472196, .949327488264e-1, -.980469816509e-2,
         .165167634970e-4, .937359795772e-4, -.12317921872e-9,
         .196096504426e-2]

    g = 1+n[11]*d/(Tc/228/Tr-1)**1.2
    for i in range(11):
        g += n[i]*d**I[i]*Tr**J[i]
    A = Na*mu**2*rho*g/M*1000/epsilon0/k/T
    B = Na*alfa*rho/3/M*1000/epsilon0
    e = (1+A+5*B+(9+2*A+18*B+A**2+10*A*B+9*B**2)**0.5)/4/(1-B)
    return e
Equation for the Dielectric constant

    Parameters
    ----------
    rho : float
        Density, [kg/m³]
    T : float
        Temperature, [K]

    Returns
    -------
    epsilon : float
        Dielectric constant, [-]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * 238 ≤ T ≤ 1200

    Examples
    --------
    >>> _Dielectric(999.242866, 298.15)
    78.5907250
    >>> _Dielectric(26.0569558, 873.15)
    1.12620970

    References
    ----------
    IAPWS, Release on the Static Dielectric Constant of Ordinary Water
    Substance for Temperatures from 238 K to 873 K and Pressures up to 1000
    MPa, http://www.iapws.org/relguide/Dielec.html