def molecular_diffusion_coeff(mw, T, mu, Vc, phi=1.0):
    """
    Estimate the molecular diffusion coefficient using the Wilke-Chang
    equation.

    .. math::  D_m = \\frac{7.4 \\times 10^{-8} (\\phi M)^{0.5} T}{\\mu V_{bp}^{0.6}}

    where:

    .. math::  V_{bp} = 0.285 \\times V_c^{1.048}

    Parameters
    ----------
    mw : float
        Molecular weight weight of solute [g/mol]
    T : float
        Temperature [K]
    mu : float
        Viscosity of the solvent [cP]
    Vc : float
        Critical volume of the solvent [cm^3/mol]
    phi : float, optional
        Association factor [-]. phi is 2.26 for water, 1.9 for methanol, 1.5
        for ethanol and 1.0 for an unassociated solvent.

    Returns
    -------
    Dm : float
        Molecular diffusion coefficient [cm^2/s]

    Example
    -------
    >>> molecular_diffusion_coeff(32.04, 298.2, 0.386, 173.0, phi=1.9)
    3.708e-5

    References
    ----------
    C.R. Wilke and P. Chang. Correlation of diffusion coefficients in dilute
    solutions. AIChE J., 1955, 1, 264–270.
    """
    Vbp = 0.285 * Vc**1.048
    Dm = 7.4e-8 * (phi * mw)**0.5 * T / (mu * Vbp**0.6)
    return Dm