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What Is a Reflux Condenser?

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  • Written By: Vasanth S.
  • Edited By: R. Halprin
  • Last Modified Date: 02 December 2014
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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.

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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).

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megh
Post 5

I have an essential oil distiller with a graham water-cooled condenser. I've got aquarium tubing hooked up to it but I can't seem to find an attachment to hook up to a water supply (e.g. my sink). Any help would appreciated!

lluviaporos
Post 3

@irontoenail - I didn't think of myself as a mad scientist so much as a general adventurer, like McGyver or something.

The experiment we did was using the reflux condenser to purify salt water, you see, and I could easily imagine doing that on a deserted island or something.

The only problem I could see was that we had to use water in order to cool down and condense the vapors, which didn't seem very efficient.

But then I realized that I was being an idiot and you could just as easily use cold salt water for that. You don't need to use tap water.

Of course, in reality I'm not likely to be able to whip out a reflux condenser if I ever got stuck on a desert island.

I'd have to make one out of coconuts and bamboo!

irontoenail
Post 2

@Mor - Actually, distillation was interesting to me because it was one of the few things we did in chemistry that I could directly relate to real life. In lots of different ways, too, although since I was a bit of a capitalist when I was a student, my mind was dancing with different schemes after we did it, like distilling the roses in my mother's garden to get rose oil to sell.

Of course, when I found out it takes something like 10,000 pounds of roses to make one ounce of rose oil, I gave up on the idea.

Even if I had managed to get together all the equipment needed for the distillation, my mother's garden would have barely given me a drop.

It's too bad, because I really fancied myself as a mad scientist as well. And a reflux condenser does seem to be a vital piece of equipment for such a profession.

Mor
Post 1

I always found distillation kind of exciting in chemistry classes at high school. I guess I really liked the idea of setting up what seemed like a fair amount of equipment (to me, as a high school student anyway) to do something that seemed like it was out of a genuine mad scientist movie.

Boiling a liquid, allowing it to separate and drip down into another container... it was interesting. And even better if you ended up with something of a different color at the end of it.

I guess I was thinking about the aesthetics of the act rather than what we were actually doing, but that's better than hating chemistry I suppose.

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