and bottom (stripping section) of the column when the starting liquid (called feed composition) is released in the middle of the column. This is shown in Figure 2. At a certain temperature, the component with the lowest boiling point (called distillate or overhead fraction) vaporizes and collects at the top of the column, whereas the component with the highest boiling point (called bottoms or bottom fraction) collects at the bottom of the column. In a zeotropic mixture, where more than one component exists, individual components move relative to each other as vapor flows up and liquid falls down. The separation of mixtures can be seen in a concentration profile. In a concentration profile, the position of a vapor in the distillation column is plotted against the concentration of the vapor. The component with the highest boiling point has a max concentration at the bottom of the column, where the component with the lowest boiling point has a max concentration at the top of the column. The component with the intermediate boiling point has a max concentration in the middle of the distillation column. Because of how these mixtures separate, mixtures with greater than three substances require more than one distillation column to separate the components. Distillation configurations Many configurations can be used to separate mixtures into the same products, though some schemes are more efficient, and different column sequencings are used to achieve different needs. For example, a zeotropic mixture ABC can be first separated into A and BC before separating BC to B and C. On the other hand, mixture ABC can be first separated into AB and C, and AB can lastly be separated into A and B. These two configurations are sharp-split configurations in which the intermediate boiling substance does not contaminate each separation step. On the other hand, the mixture ABC could first be separated into AB and BC, and lastly split into A, B, and C in the same column. This is a non-sharp split configuration in which the substance with the intermediate boiling point is present in different mixtures after a separation step. Efficiency optimization When designing distillation processes for separating zeotropic mixtures, the sequencing of distillation columns is vital to saving energy and costs. In addition, other methods can be used to lower the energy or equipment costs required to distill zeotropic mixtures. This includes combining distillation columns, using side columns, combining main