[Kaladiscope]

I'm going to run an experiment and I read that I have to use a reflux condenser. What I can not really understand is that afterwards is mentioned in the procedure "Do not circulate cold water when you do the refluxion".

It does make sense? As far as I know one always have to pass cold water in order to avoid the evaporation of the solvents....

[discodermolide]

I'm going to run an experiment and I read that I have to use a reflux condenser. What I can not really understand is that afterwards is mentioned in the procedure "Do not circulate cold water when you do the refluxion".

It does make sense? As far as I know one always have to pass cold water in order to avoid the evaporation of the solvents....

Which solvent is it?
You can use an air condenser, especially for higher temperatures.

[408]

half the time my condensers are dirty, so instead of washing them I just put a 1m long glass tube on top of the refluxing flask.  Lower boiling solvents need a longer tube.  I am lazy, but this works just as well as any condenser.

[discodermolide]

half the time my condensers are dirty, so instead of washing them I just put a 1m long glass tube on top of the refluxing flask.  Lower boiling solvents need a longer tube.  I am lazy, but this works just as well as any condenser.

I don't subscribe to that philosophy, on larger scale that can be dangerous.

[Kaladiscope]

I am using as a solvent dimethoxyethane (ethyleneglycoldimethylether). In the procedure it saids...

"If you pass cold water the vapors of 1, 2 – dimethoxyethane will be staying down and there won’t be leaching"

[discodermolide]

I am using as a solvent dimethoxyethane (ethyleneglycoldimethylether). In the procedure it saids...

"If you pass cold water the vapors of 1, 2 – dimethoxyethane will be staying down and there won’t be leaching"


[/quote

This has a BPt. of 85°C.
"Leaching" of what? Sorry that makes no sense.

[orgopete]

The boiling point is reasonably high so it shouldn't be difficult to avoid evaporation. I am guessing the condenser has been packed with something they are extracting with dimethoxyethane. Water will keep the dimethoxyethane from reaching the top of the packing. Did I guess it?

[discodermolide]

The boiling point is reasonably high so it shouldn't be difficult to avoid evaporation. I am guessing the condenser has been packed with something they are extracting with dimethoxyethane. Water will keep the dimethoxyethane from reaching the top of the packing. Did I guess it?

If that is the case it may be easier to use a soxhlet extractor.

[fledarmus]

The only time I haven't been able to use cold water in a reflux condenser is when I am using a solvent that is a solid at 20C. Tert-butanol caught me a couple of times, and one winter night I had a problem with acetic acid.

[orgopete]

Well, if we are going in that direction. I'll bet there is more than one lab that had a flood when the water pressure changed or something expected happened in which the water hose became disconnected. I know I always had a level of anxiety anytime I ran a condenser overnight (I never had a flood either). A faster reflux doesn't increase the temperature, so I always tried to have the minimal amount of heat needed.

Re: Soxhlet, I think this is a student prep. Soxhlet seems like overkill. I've used addition funnels in place of Soxhlets too.