Setup for purification of solvent (here: tetrahydrofuran over sodium/benzophenone)

The standard setup consists of a round bottom flask that is charged with a solvent and the drying agent, a collection flask, a reflux condenser (it can't be seen here because it is in the upper part of the fume hood) and a heating mantle. The heating mantle is connected to a flow switch device that controls the power output. If the cooling (water flow) stops, it shuts down the power immediately. When it comes to drying solvents, there are several things to consider:

1. The solvent purification setup has to be well maintained. The flask has to be clean in regular intervals. The remaining drying agent has to be quenched properly and disposed off. Solvent stills that have been operated for too long without maintainance mean a serious safety risk. Bases slowly dissolve the glass of your flask! In addition, the remainder of the drying agent are difficult to deactivate if covered with a lot of byproducts.

2. Make sure that you use the appropriate drying agent for your solvent. If you are not 100% sure, better check before you blow yourself up. It is not uncommon that mistakes in this regard led to serious explosions and accidents. See also Drying solvents.