An apparatus for separating a gas from a liquid but truly suited for use in a zero gravity environment. The apparatus includes first and second closed vessels each of which are separated into a gas and liquid zone. The first vessel is separated by gas de-entrainment means and the second vessel by a plurality of elongated passageways for capillary containment of a body of liquid. The passageways provide the sole source of fluid communication between the gas and liquid zones. The gas zones of the first and second vessels are in fluid communication with one another as are the liquid zones of the first and second vessels. Means are provided for introducing a liquid containing entrained gas into the first vessel for impingement upon the gas of the entrainment means such that the liquid passes through the de-entrainment means and flows into the second vessel and the entrained gas is separated and flows into a gas storage space of the second vessel displacing the body of liquid metal contained in the passageways in said second vessel. The apparatus further includes means for withdrawing liquid from a liquid zone of the second vessel which has been freed of any entrained gas. The apparatus is particularly suitable for use in the separation of tritium and helium from the lithium coolant of a nuclear reactor.