The results presented in previous sections are purely linear phenomena. In addition, distillation columns have important nonlinear effects. For example, even an infinite reflux rate (requiring an infinite vapor boil-up rate) will yield a mole fraction of the light component in the distillate that is less than 1.0. If the steady-state value of the distillate composition is 0.99, it can increase by less than 0.01, yet it can decrease to almost as low as the feed composition of 0.5. The range for increasing purity is then much smaller than the range for decreasing purity.