AbstractBefore 1939 the only practical method of converting sea water into drinking water Was by distillation. This method, whilst subjected to improvement during the war, could not be applied for use in the rubber dinghies in which stranded aircrews must exist until they are picked up. For the reason an alternative method was essential and a chemical means of removing the dissolved salts from sea water was developed which was simple in operation and which provided a largo margin of dunking water over that which could be carried in tilts in the emergency packs.This article describes the development of the process and the results finally achieved. Furthermore, it shows how the properties of ion exchange materials, which in peacetime hud been used mainly for softening hard waters, could be applied to other purposes und assist in the solution of an otherwise difficult chemical problem.