Gas inlet tube

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A simple gas inlet tube with a red plastic screw cap

A gas inlet tube (also called long-stem hose inlet adapter, long-stem gas inlet tube, gas admission tube) is a piece of lab glassware used in chemical processes to inject a gas in a closed system, most often in a liquid, either during boiling or in an inert atmosphere, or in gas washing bottles.


Gas inlet tubes have the appearance of a thistle tube, but with a male ground glass joint and a hose barb, the latter being either made of glass or plastic, though some models have a separate gas inlet adapter, which can be connected to the female ground glass joint of the inlet tube. Some models also have a stopcock to regulate the air flow.

A more often encountered type of gas inlet tube has two upper glass tubes, a long one through which gas is injected in the liquid or bottle, and an external one, through which the excess gas is evacuated from the bottle. This piece of glassware is often used in gas washing bottles and cold traps.

While similar in construction to gas dispersion tubes, gas inlet tubes aren't generally used in chemical reactions between the gas and the liquid/dissolved solid, as they do not offer good gas dispersion. They're more often used in steam distillation and gas sparging.


Gas inlet tubes can be purchased online from lab suppliers, tough they're not easy to find.

DIY gas inlet tube

A simple gas inlet tube can be made by inserting a thin glass tube through a stopper or a thermometer adapter, and connecting the outer end of the tube to a hose. If the reaction does not involve corrosive reagents, you can also use metal tube and if the process doesn't require high temperatures, you can also use plastic tube.


See also


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