Addition of solids to Schlenk tubes

There are a number of ways to add solids to Schlenk tubes, with some of the considerations being:

• The air-stability of the compound in question

• The compounds volatility

• Whether it is being added to an empty tube or to a solution

The most common addition is for an air-stable solid to an empty Schlenk tube and this is the process described in detail. The addition of solids to solutions is possible, however this is more commonly achieved by the dissolving of the solid in solvent and the addition of this new solution to the original solution via cannula transfer (see later for this technique). For air-unstable solids, this addition is usually achieved using a glove-box, which is not described here.

Addition of an air-stable solid to an empty, purged Schlenk tube

These instructions apply to an empty socket and stopper Schlenk tube. The instructions require minor amendments when used with cone & helmet flasks.

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, then the stopper can 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. The form of the solid needs to be considered prior to attempting addition. Very fine powders are liable to be aerosolised if poured into the stream of gas exiting the flask, and the gas flow may need to be regulated or stopped entirely. However, for most solids it is possible to then pour the solid sample directly into the Schlenk tube via the socket. It may be desirable to use a funnel, in order to extend the point of addition beyond any grease in the socket. Care should be taken to avoid any solid material becoming stuck in the grease, as this will prevent a good seal being made with the stopper, and may cause damage to the glassware (e.g. by scoring it).

3. The Schlenk tube should be promptly resealed by reinserting the stopper and twisting it to ensure a good seal in the grease. Pay attention to the oil bubbler during this process as it should resume bubbling now this forms the path of least resistance to gas flow.

4. For non-volatile solids, it is possible to repeat the vacuum/gas cycles to ensure that the flask is fully under inert conditions. However, if a solid is at all volatile, this is ill advised.