Use of balloons for holding an inert atmosphere

Although we recommend using the double manifold techniques described above, reactions can also be kept under inert atmosphere by using a balloon filled with inert gas (Fig. 9.10). This can prove particularly useful if a 

In the case of the needle/septum attachment, any air contained in the reaction flask is then flushed out by using another needle to vent the system (Fig. 9.11). After the reaction flask has been thoroughly flushed with the inert gas, the extra needle is removed and the reaction flask is ready for use. The balloon keeps the whole system under a positive pressure of the inert gas, and also allows liquid materials to be added to, or removed from, the flask via syringe insertion through the septum. 

Generally argon is preferred when using this technique because it is more dense than air, and will fill the reaction flask, pushing out any air more effectively than would nitrogen. This technique can also be employed when syringing air-sensitive materials from bottles or containers. 

With the three-way tap attachment, a vacuum line can be connected (Fig. 9.10). The system can then be purged by sequentially evacuating, then filling with the inert gas from the balloon. This is a more effective 

Since balloons are perishable it is often advisable to use a double balloon system. This is simply two balloons, one inside the other, allowing the inert atmosphere to be maintained even if one bursts. 

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