def rho_bot_vap(t_boil_y_bot, T0, Vm, M_bot_vap):
    """
    Calculates the destiny of vapor at the bottom of column.
    Parameters
    ----------
    t_boil_y_bot : float
        The boilling temperature of low-bolling component of vapor at the bottom of column, [C]
    T0 : float
        The initial temperature, [K]
    M_bot_vap : float
        The molar mass at bottom of column, [kg/kmol]    
    Returns
    -------
    rho_bot_vap : float
        The destiny of vapor at bottom of column, [kg/m**3]
    References
    ----------
    Романков, стр.13, формула 1.5
    """            
    return (M_bot_vap / Vm) * (T0 / (T0 + t_boil_y_bot))