Abstract: In the single column process for the recovery of nitrogen from air wherein reflux for the distillation is provided by condensing a first portion of the overhead stream by indirect heat exchange in a reflux condenser with oxygen-rich liquid from the bottom of the column which has been subjected to a first expansion to an intermediate pressure, refrigeration for the process is provided by work expanding evaporated oxygen-rich liquid from the reflux condenser, and prior to said first expansion, the oxygen-rich liquid recovered from the bottom of the column is sub-cooled by indirect heat exchange in a sub-cooler with the work-expanded evaporated oxygen-rich liquid, nitrogen recovery is increased by work expanding the evaporated oxygen-rich liquid at a temperature not substantially greater than that at which it is recovered from the reflux condenser or by first passing it through said sub-cooler at a temperature not substantially greater than that at which it is recovered from the reflux condenser and thereafter w