Sample tube for gas awaiting analysis by chromatography - holds a little inert liquid to improve its membrane seal

摘要

The sample tubes are sealed by an elastic membrane held in place by a screw cap; the cap has a small hole, through which a hollow needle can be passed to fill the tube or to remove its contents. The tube contains a little liquid, chemically inert w.r.t. the gas to be stored, which lies in a layer above the membrane when the tube is inverted and so improve the seal. The tube is normally filled membrane upwards. The cap may be perforated for a second hollow needle so that any residual contents may be flushed out of the tube before the gas to be preserved is introduced. Mercury is suitable liquid to use.