def vapor_phase_sat_conc(MW, vapour_pressure, temperature, R=8.314):
    """
    Return the vapor phase saturation concentration [kg/m³]

    Parameters
    ----------
    MW : Molecular weight [kg/mol]
    vapour_pressure : Vapour pressure [Pa]
    T : Temperature [K]
    R : Perfect gas constant, the default is 8.314 [J/mol K]
    source:ALOHA

    """
    return MW * vapour_pressure /(temperature * R)