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Topic: Reflux experimental q. If it is refluxing, does it have to condense?  (Read 2722 times)

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Offline radonreds

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I'm refluxing a solution with methanol as a solvent. I have the temp a little above its boiling point. It is dripping, like 1 every 6 seconds., but nothing is condensing in the  condensing tube.

I've never used methanol as a solvent for reflux, so I was wondering if this is specific to methanol?

FYI Bp of methanol ~80c I have it at 95c . I don't want to force it above 110c, but nothing is condensing.

Offline discodermolide

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Re: Reflux experimental q. If it is refluxing, does it have to condense?
« Reply #1 on: September 25, 2012, 11:07:44 AM »
Turn the condenser water on.
It should condense but the heating object up to 100°C.
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Offline radonreds

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Re: Reflux experimental q. If it is refluxing, does it have to condense?
« Reply #2 on: September 25, 2012, 11:49:33 AM »
The condenser's water is on. I'm Not that terrible. Water is running through the tube, the reflux is dripping. It is just not condensing in the tube.
All the reflux methods I've read, say once you start the reflux don't allow it to condense more that half way up the condenser . But what if its not condensing at all? I feel like it should be fine. But i really would hate to do this reflux again(5hrs). That's why I need y'all advice?

Offline discodermolide

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Re: Reflux experimental q. If it is refluxing, does it have to condense?
« Reply #3 on: September 25, 2012, 11:59:17 AM »
Just increase the temp. to 100°C and then it should be fine.
You could also wrap the flask and lower condenser surfaces with aluminium foil.
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Offline DrCMS

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Re: Reflux experimental q. If it is refluxing, does it have to condense?
« Reply #4 on: September 25, 2012, 12:01:00 PM »
If you have a condensor attached to the top of your flask and you can see liquid dripping out of the condensor back into the flask then the methanol vapour is condensing. 
Where else do you thing the liquid is magically apprearing from.

Also methanol has a boiling point of ~65°C so unless you have a lot of material dissolved in it to elevate the bp that much stop heating it so hard as you could be losing methanol out of the top of the condensor.

Offline orgopete

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Re: Reflux experimental q. If it is refluxing, does it have to condense?
« Reply #5 on: September 26, 2012, 07:34:53 AM »
Except for the temperatures being reported, I would have said this was an ideal description of a safe description of a refluxed reaction. Even if the temperature of the heating source was increased and thus the distance into the condenser that condensation occurred also increased, the temperature of the reaction is not. If you ran the reaction for a long time and unattended, I prefer a lower rate of reflux. If you have a high reflux rate and should the water flow through the condenser change, two common results are loss of solvent or a flood.
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