Video: Introduction to Refluxing
The video below provides a brief introduction to the concept of refluxing and the apparatus setup.
Reflux Description
Many reactions are carried out at elevated temperature in a boiling solvent. To prevent the solvent from evaporating while the reaction proceeds, a condenser is placed on top of the vessel (Figure 1). Although there are several types of condensers, the most common is a water-cooled condenser that has an inner tube surrounded by a jacket through which tap water flows. As the vapors from the reaction mixture travel up through the cooler inner tube, they condense and flow back to the reaction vessel. This process is called refluxing.
Figure 1. Typical reflux apparatus. The heat source may vary.
• Be sure to connect the condenser to the flask with a Keck clamp (blue plastic clamp).
• Be sure to use a utility clamp to secure the flask or condenser to a ring stand or “monkey bars” in the hood.
• Be sure to connect the water hoses such that water flows into the condenser through the lower port and out through the upper port.
• Be sure you choose an appropriate heat source based on the required temperature. Boiling temperature is generally best achieved by using a heating mantle, and a steady temperature below 100°C is generally best achieved using a hot water bath on a hot plate.
• If using a water bath, the copper pots heat quickly and hold a steady temperature well. The temperature may be monitored using a thermometer and a thermometer clamp.
• If heating with a heating mantle (Figure 2), be sure there is a snug fit between the flask and the heating mantle in order to achieve efficient heat transfer.
Figure 2. A heating mantle