Oil bubbler

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A simple oil bubbler.

An oil bubbler is a piece of laboratory glassware which consists of a glass bulb filled with a small amount of silicone oil. The inlet to the bulb is connected to a ground glass joint, while the outlet is vented to the air.

Oil bubblers are used to exclude air from a reaction or a system. In the former case, the oil bubbler is fitted on the condenser of the reaction set-up. In the latter case, an oil bubbler is usually installed at the end of the inert gas manifold on a Schlenk line to prevent contamination by atmospheric oxygen and water.

The oil bubbler acts as a one-way valve - gases (hot air, evolved gases, solvent vapors) from the inlet will bubble through the oil before being vented to the atmosphere. On the other hand, if there were an underpressure in the reaction vessel (such as when heat is removed, and the gases within contract), oil is sucked into a sump to equalize the pressure, instead of air. Wherever possible, such "suck back" should be avoided by filling the reaction apparatus with inert gas because an excessively low pressure will cause oil to be sucked into the reaction vessel, contaminating it.

[edit] Mercury bubbler

Mercury bubblers are similar to oil bubblers. The high density of mercury increases the pressure of the gas flowing through the line, since more force is required for the gas to bubble through such a dense material. However, due to the mercury's toxicity, and the risk of releasing large quantities of mercury if the bubbler were to be broken or sucked back into the gas line, the use of mercury bubblers is generally discouraged. In addition, mercury can react with various chemicals, such as ammonia and acetylenes, with potentially hazardous results[1]. Oil bubblers are usually adequate substitutes.^{[citation needed]}