Control method to maximize argon recovery from cryogenic air separation units

In a process for the separation of mixtures, which comprise oxygen, nitrogen, and argon, by cryogenic distillation in a distillation unit comprising an argon sidearm column with an overhead condenser and a low pressure column, wherein the argon sidearm column integrally communicates with the low pressure column, the improvement for increasing argon recovery comprises reducing the pressure of feed gas withdrawn from a lower-intermediate location of the low pressure column and fed to a lower location of the argon sidearm column whereby the operating pressure of the argon sidearm column is controlled at the lowest effective pressure which is consistent with a minimum temperature difference across the overhead condenser and an unrestricted return of crude oxygen vapor from the overhead condenser of the argon sidearm column to the low pressure column.