Consider a feed containing a binary mixture of compounds A and B with 45 mole % of the lighter component. This stream is a saturated liquid, which will be fed to a stripping column in order to obtain a bottom with 15 mole % purity. Stripping columns are used when a pure distillate is not needed. This Demonstration displays the McCabe–Thiele graphical construction for user-set values of the reboil ratio and relative volatility. The actual number of stages is easily obtained by inspection of the diagram. In addition, the composition of the vapor stream that exits at the top of the stripping column is computed and given in the set-up figure.