Abstract: Apparatus comprising a source of a first fluid (204), a fluid displacement device (210) for moving the first fluid from the source to a sealed storage chamber (214), means for introducing a second fluid (207), different from the first fluid into the first fluid prior to reaching the storage chamber, the arrangement being such that the sealed storage chamber receives a mixture of the first and second fluids under a pressure greater than the pressure at the point at which the second fluid is introduced into the first fluid and includes a first fluid outlet (220) for directing the first fluid separated from the second fluid in the storage chamber externally of the storage chamber.