Abstract: The maximum profit policy in the operation of a batch distillation column separating a binary mixture has been studied. A generalized mathematical model was derived with consideration of tray efficiency and liquid hold-up in the plates and the condenser. The optimal scheme of reflux control was worked out by a digital method. Computation showed that the proposed optimal control scheme could lead to much higher profit than the conventional mode of operation using constant reflux ratio or constant overhead composition. To demonstrate the practical usefulness of the proposed scheme, experimental work was conducted for the separation of ethanol-water mixture in a 0.17 meter diameter batch distillation column which was operated both under the optimal reflux control scheme and according to the conventional mode of constant reflux ratio. The economic profit obtained from the former operation was found to be 207% higher than that from the latter, the theoretically predicted value being 220%.