A reflux condenser is a laboratory glassware that is used to cool vapors. It consists of a glass tube encased in a glass cylinder. The tube connects the fractioning column with a flask and carries hot vapors produced from heating. Water is contained the glass cylinder; the water is pumped in and out of the cylinder through its side arms. The water cools the vapor within the tube and condenses it. The are two kinds of reflux condensers.
As the vapor condenses, it flows back into the reaction flask. This reduces the amount of solvent that is lost during the reaction. In addition, the reaction can be carried out over an extended period of time since the solvent is recycled back into the reaction flask.
The condenser is mainly used in the distillation process. A distillation is the separation of two liquids by heating. The liquid with the lower boiling point will vaporize first. It is converted back into a liquid inside the condenser. If the condenser deposits the liquid back in the reaction flask, it is called a reflux condenser.
There are two types of reflux condensers: air cooled and water cooled. The common air cooled reflux condensers include the air condenser and the Vigreux condenser. A Liebig condenser is the simplest water cooled reflux condenser. The Dimroth condenser and the Graham condenser are two other water cooled reflux condensers.
The air cooled reflux condenser only has one glass tube, and the vapors condense on the glass as they are cooled by the air. Some air cooled reflux condensers are filled with glass beads to aid in the condensation process. The Vigreux condenser features a series of indentations designed to increase the amount of surface area available for the vapor to condense on.
A water cooled reflux condenser has two glass tubes. The inner tube carries the hot vapor, while the outer tube carries the water. Water is used to cool the vapor. The Liebig condenser features a straight inner tube, while the Graham condenser has a spiral inner tube. There is a double spiral tube within the Dimroth condenser.
Generally, water is used to cool the vapor in water cooled reflux condensers, but there are other solvents which can be used to cool the vapor. These include ethanol and a dry ice and acetone mixture. These solvents are typically used when the reaction involves liquids which boil at a temperature that is below 32° F (0° C).