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Bubblers

Bubblers provide a pressure relief system within the Schlenk line as well as allowing the inert gas flow rate to be easily monitored. Bubblers act as a one-way valve to allow gas to escape the inert gas manifold, whilst preventing atmospheric air and moisture contaminating reactions on the Schlenk line. Several types of bubbler are commonly used in the laboratory, all of which have their own advantages and disadvantages.

Oil Bubblers

Oil bubblers are perhaps the most common bubblers employed in research and teaching laboratories, primarily due to their simplicity and low cost. They are filled with silicone or mineral oil, which have high chemical resistance. The major drawback of oil bubblers is their susceptibility to ‘suck back’ when backfilling evacuated flasks with inert gas, or when cooling flasks without first increasing the gas flow. This can easily contaminate the reaction vessel with atmospheric air and moisture, or even suck oil into the inert gas manifold of the Schlenk line. Another disadvantage of oil bubblers is the reduced inert gas pressures in the Schlenk line due to the low density of the oil. This means that cannula transfers and cannula filtrations are typically quite slow.

A typical oil bubbler.

Over-Pressure Bubblers

Over-pressure or pressure-relief bubblers are oil-based bubblers that contain a spring-loaded valve mechanism which allows for fine control of the inert gas pressure within the Schlenk line. This design also prevents oil suck back. When used in tandem with a regulator, the over-pressure bubbler can be adjusted to relieve pressure only when exceeding a set limit, meaning that high inert gas pressures can be safely reached, enabling faster cannula transfers and cannula filtrations. The major disadvantage is the high cost compared to simpler oil bubbler designs.

An over-pressure bubbler.

Mercury Bubblers

Mercury bubblers work on a similar principle to oil bubblers but provide much higher inert gas pressures within the Schlenk line. The pressure can be manually controlled to increase the gas flow during certain manipulations by partially blocking the exhaust tubing with a finger or thumb. Mercury bubblers are often over 76 cm in height (1 atmosphere can support 760 mmHg) which allows the inert gas manifold to be fully evacuated under vacuum, rather than being flushed or purged with inert gas. The major disadvantage with mercury bubblers is the health and safety issues concerned with handling mercury and disposing of waste. Mercury is also incompatible with many chemicals that may be used on the Schlenk line. Note: Appropriate safety and containment measures must be in place when using a mercury bubbler.

Bubblers provide a pressure relief system within the Schlenk line as well as allowing the inert gas flow rate to be easily monitored. Bubblers act as a one-way valve to allow gas to escape the inert gas manifold, whilst preventing atmospheric air and moisture contaminating reactions on the Schlenk line. Several types of bubbler are…

What is an oil bubbler (gas bubbler)? When is it required?

An oil bubbler (also called a gas bubbler) is a common piece of general laboratory glassware, which is part filled with oil and vented to the atmosphere.

Oil bubblers are generally used to prevent pressure build-up while maintaining an inert atmosphere inside a vessel. Gas passes (bubbles) out through the bubbler, but air does not pass back through the bubbler to the reaction. The bubbler therefore acts as a one-way valve. Oil bubblers also provide a way to view the rate of gas flow.

Radleys tend to sell oil bubblers for use with jacketed lab reactors (such as Reactor-Ready) for work under nitrogen etc., as it is important not to pressurise glassware (as described in the separate FAQ entry on jacketed lab reactors and pressure).

You may find bubblers in the lab set up with Schlenk lines (vacuum-gas manifolds).

Our standard part numbers are as follows; alternative joint sizes (and designs) are available:

  • RR139051: Oil Bubbler Type 1 B24 + GL14 + fittings
  • RR139314: Oil Bubbler Type 1 B29 + GL14 + fittings

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What is an oil bubbler (gas bubbler)? When is it required? An oil bubbler (also called a gas bubbler) is a common piece of general laboratory glassware, which is part filled with oil and vented ]]>