This Demonstration leads the user through a step-by-step procedure to construct an x-y diagram for a trayed absorption column that is used to remove an impurity from a gas feed by absorbing the impurity in a liquid solvent. The number of trays/stages needed to obtain a desired outlet concentration in the gas stream is calculated. Click the “new problem” button to create a different set of conditions and reset the Demonstration. Click “next” to go to the next step. Check “hint” for a hint, and check “solution” to see the solution before selecting next step.