Assembling a Schlenk flask

Typically, Schlenk flasks are kept in ovens to minimise the presence of any residual water from the atmosphere. The Schlenk flask has a tap which will need to be fitted after the flask has been removed from the oven. Any ground glass joints on the flask will need to be greased to ensure a good vacuum seal when connected to the line.

There are many tap designs, including the use of glass, Teflon and Youngs tap designs. It is important to check the right tap is being fitted into a flask. In the photos below, look how the hole through the tap correctly lines up in the first image, but the hole doesn't line up in the second. It is also important to use the correct fittings which may accompany the tap. Ensure you are familiarised with the specific flask designs in use, and know how to assemble the flasks correctly.

2. Obtain the Schlenk flask. Note these are often oven-dried in order to minimise water content. Where flasks are oven dried, it is nescessary to be prompt with assembly, so that the flask can be evacuated/back-filled whilst the flask is still warm.

3. Grease the tap and insert into the tap joint. The tap needs to be effectively greased, such that it will turn freely, including when under vacuum. Guidance for greasing joints can be found on the Greasing joints on a Schlenk flask page.

4. Connect the plastic fittings onto the tap. The order of the fittings is important and is specific to the tap design.

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