This Demonstration dynamically simulates a distillation column with 32 stages. A distillation column is the most ubiquitous unit operation in a chemical plant. It allows the separation of chemical species of a mixture based on their relative volatility. The simplest distillation problem treats binary mixtures with constant relative volatilities. The dynamic study of a distillation column allows the prediction of the behavior of the distillate and bottom compositions when, for example, there is a change in the reflux ratio. This study is also useful for control purposes when, for example, some actions are taken to keep the distillate purity constant despite perturbations in the system. Here, the initial condition is a steady state with a reflux ratio of 3, and the curves trace out the changes over time to the mole fractions in each stage when the reflux ratio is changed to a new value.