Jack Edwin Bissey California State College 10s Angeles
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Versafile Bubbler Valve
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This device was developed to control nitrogen pressure as the gas was admitted to a vacuum system. When nitrogeu was bled slowly mto an evacuated desiccator the lid "popped" off and flew a foot into the air. Obviously the gas pressure exceeded one atmosphere before the lid parted from the sealant. A bubbler valve overcomes the uncertain nature of this technique. The valve (see figure) is an ordinary gas bubbler with the refinement of a mercury check-valve of the type used in laboratory vacuum lines. A groundglass joint allows easy dismantling for cleaning. The valve operates as follows. The desiccator is connected with a vacuum hose at B. The three-way valvo D is turned to apply a vacuum a t A. This causes the mercury in the reservoir to rise in the central tube, closing check-valve V. Thus the connecting line to the desiccator is evacuated. Then the desiccator (under vacuum) is opened to the connection (under vacuum). Next, valve D is turned so that nitrogen enters at A. When the nitrogen pressure equals one atmosphere, check-valve V drops and excess nitrogen bubbles out through C. The lightly packed glass wool in the bubbler head prevents mercury from spattering out the opening C. This device has numerous applications. I n experiments using glass pressure tubes, it is necessary to insure that no air or water is in the tuhe prior to use. Usually the tubes are baked in an oven and then flushed
out with nitrogen for five minutes. This is both wasteful of nitrogen and uncertain. With the bubbler valve, a vacuum is applied to the tube and it is flamed out to remove traces of water. Nitrogen is then bled in and observation of the dropping of check-valve V tells when the tuhe contains nitrogen at one atmosphere. For reactions and distillations conducted in an inert atmosphere the apparatus can be evacuated and then filled with nitrogen as usual; the bubbler is left on to function in its ordinary role as an indicator of the pressure of inert gas in the system. The bubbler valve is ideal for releasing the vacuum at the conclusion of a vacuum distillation. Vessels or systems may be filled with noxious or corrosive gases to a pressure of one atmosphere in like manner; outlet Cis then connected by hose to a hood.
Volume 42, Number 6, June 1965 / 317
