def xdist_molar(xdist_mass, Massl, Massh):
    """
    Calculates the molar concetration distilliat of liquid.
    Parameters
    ----------
    xdist_mass : float
        The mass concetration distilliat of liquid, [kg/kg]
    Massl : float
        The molar mass of low-boilling component, [kg/kmol]
    Massh : float
        The molar mass of high-boilling component, [kg/kmol]
    Returns
    -------
    xdist_molar : float
        The molar concetration distilliat of liquid. [kmol/kmol]
    References
    ----------
    Романков, страница 282, таблица 6.1 / Дытнерский стр.228 формула 6.3
    """ 
    return xdist_mass * Massh / ((xdist_mass * Massh) + (Massl - Massl * xdist_mass))