def Diff_liq(Diff_20, b, t_boil):
    """
    Calculates the diffusion coefficient of liquid phaze.
    Parameters
    ----------
    calc_Diffcoef20 : float
        The diffusion coefficient at 20 degrees celcium, [m**2/s]
    b : float
        The temperature coefficient, [dimensionless]
    t_boil : float
        The boiling temperature of liquid, [degrees celcium]
    Returns
    -------
    Diff_liq : float
        The diffusion coefficient of liquid phaze.
    References
    ----------
    Романков, страница 289, формула 6.23
    """
    return Diff_20 * (1 + b * (t_boil - 20))