Addition of liquids and solvents to Schlenk tubes

Liquids and solvents can be added to Schlenk tubes by replacing the stopper on the Schlenk tube with a septum which then allows the insertion of needles through the septum in order to add liquid reagents and/or solvents. The process of drawing up liquids should already be familiar to you, and the instructions below focus on the Schlenk tube preparation, rather than the details for using a syringe.

1. With an empty Schlenk tube which has been purged and refilled with inert gas, ensure that the oblique tap connects the flask to the gas line and that the tap to the Schlenk tube is open. Only then should the stopper be carefully removed. The flask will remain under an inert atmosphere, as the positive gas pressure will exit the flask via the socket, as this will be the path of least resistance for the gas. Consequently, the bubbler will stop bubbling.

2. Insert a septum into the joint and the oil bubbler should resume bubbling. For socket joints it is ideal to quickly wipe off the excess grease before inserting the septum. For cone joints, you could use the septum upside down over the cone (though the seal will not be great), however, with patience septa can be fitted in the usual way but you will need to support the flask with your other hand as it will feel quite tight when you’re first pushing it in.

3. Keeping the flask connected to the gas line, syringe in the desired solvent and/or liquids. Try to ensure that no air is introduced into the Schlenk tube via the syringe.

4. Once the syringe work has been completed, the septum can be removed and the flask resealed with the stopper or helmet. This should be done under a flow of nitrogen and watching the bubbler as in steps 1 and 2).