Prove that for ideal systems (constant relative volatility) with no interaction between an added noncondensable, nonsoluble gas and the condensable components, there is no effect of adding the noncondensable, nonsoluble gas on liquid mole fractions at equilibrium; however, the dew-point temperature is decreased. Most systems are not ideal, and the added noncondensable, nonsoluble gas will change the liquid mole fractions.