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B.D.E
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[*] posted on 24-1-2020 at 15:37
Graham condenser - explosion hazarded?


Hey there,
I recently read(somewhere in the forum) that refluxing with a Graham condenser might cause pressure buildup due to condensed liquid clogging the coil. The explanation was that the gas pressure might prevent the condensed liquid from falling down.

Before reading about it I've ordered a soxhelt extractor with, you guessed it, a Graham condenser.
condenser.bmp - 213kB

I wanted to ask if the risk is real, and if so in which cases? Also, is there anything I can do to minimize the risk down to negligible levels?

As the soxhelt extractor is expected to run for long periods of time without supervision, I obviously want to make sure it safe to use it.

Much thanks, Ben.
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XeonTheMGPony
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[*] posted on 24-1-2020 at 16:53


don't use a gram for that very stupid idea them selecting that type IMO, use an Allihn condenser or Dimroth for best result.

https://en.wikipedia.org/wiki/Condenser_(laboratory)#Allihn_condenser

I ordered a converter to standard 24/40 for that reason.

[Edited on 25-1-2020 by XeonTheMGPony]
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SWIM
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[*] posted on 24-1-2020 at 20:08


I wouldn't call it an explosion hazard so much as a potential geyser.

But I agree with the above post.

I've seen those graham type condensers on Chinese Soxhlets for some time now and I've always wondered if they work okay or not.
Nanshin makes ones like that, or at least did a couple of years ago.

When switching condensers on a Soxhlet, remember that Soxhlets are meant to reflux very fast to get the job done 'quickly', so you'll want to be sure the replacement condenser has plenty of capacity.

Friedrichs condensers are popular, as are the much cheaper Alihns.

If you've got two Liebigs you can try using both on a Claisen adaptor.
I think that would be better than just stacking them but maybe my reasoning is off.




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XeonTheMGPony
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[*] posted on 25-1-2020 at 06:47


Quote: Originally posted by SWIM  
I wouldn't call it an explosion hazard so much as a potential geyser.

But I agree with the above post.

I've seen those graham type condensers on Chinese Soxhlets for some time now and I've always wondered if they work okay or not.
Nanshin makes ones like that, or at least did a couple of years ago.

When switching condensers on a Soxhlet, remember that Soxhlets are meant to reflux very fast to get the job done 'quickly', so you'll want to be sure the replacement condenser has plenty of capacity.

Friedrichs condensers are popular, as are the much cheaper Alihns.

If you've got two Liebigs you can try using both on a Claisen adaptor.
I think that would be better than just stacking them but maybe my reasoning is off.


I like the Allihn's, very easy to clean, good surface area and internal volume, the volume being most important to allow the condensate to pass over the vapor rushing in.

The Dimroth I'd be worried any bumping could rattle the tubes enough to break, same reason the gram seems like very poor selection
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stoichiometric_steve
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[*] posted on 25-1-2020 at 07:17


Quote: Originally posted by XeonTheMGPony  

The Dimroth I'd be worried any bumping could rattle the tubes enough to break


I've never seen that happening. Have you?

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[*] posted on 25-1-2020 at 07:18


Quote: Originally posted by stoichiometric_steve  
Quote: Originally posted by XeonTheMGPony  

The Dimroth I'd be worried any bumping could rattle the tubes enough to break


I've never seen that happening. Have you?



I never said I saw it, I said I'd be worried.
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B.D.E
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[*] posted on 28-1-2020 at 11:37


Thanks for the replies. I think I'll just buy another condenser(or an adapter).
I likely to be using this apparatus with ether extractions. A potential geyser of ether near an hotplate with high(ish) pressured ether-containing-RBF on top of it... It's just too much of a risk...

I am however might check it's limits just for fun(I really curious to see how much of an issue it really is).
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DavidJR
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[*] posted on 28-1-2020 at 13:46


Graham condensers are absolutely useless for reflux (and not very good for distillation in most cases either). Don't buy one of those. On the other hand, a coil condenser (coolant through coiled tube, vapour around the outside of the coil) works very well.
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morganbw
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[*] posted on 28-1-2020 at 15:30


I use one sometimes in a vertical position as a condenser for low boiling stuff.
I have had fairly good luck.

To be sure they are not a normal condenser and as for reflux, just don't do it.
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[*] posted on 28-1-2020 at 15:51


That is their main purpose, for low boiling substances where you need high efficiency low flow.

but for much of any thing ells ya, they are crap, impossible to clean so on.
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[*] posted on 29-1-2020 at 10:52


The only thing I use my Graham condenser for is when I distill bromine or diethyl ether. It works beautifully for those, but it's overkill for anything else that I've ever needed to distill. It's one of those pieces of glassware that if you're offered one for free, you should absolutely take it, but unless you're planning on setting up a large scale bromine still, you don't need to go out of your way to buy one.



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[*] posted on 29-1-2020 at 14:17


If you prefer an Allihn condenser for the Soxhlet, I have some extra conensers that fit most every size Soxhlet made. The Soxhlet's get broken way easier, so I have extra condensers. They are the best, short of a really big reflux one or a double condenser (jacket outside and coil inside), which I have a few of, but they are fragile and expensive. Note that using an adapter from 40/38 to 24/40 and a 24/40 condenser will almost certainly limit you a lot, as the condenser will just be too small to work well. There is a reason that most Soxhlets have larger diameter condensers on top, which is becasue they are needed to work well. Vapors need a lot of surface area to condense quickly.
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[*] posted on 29-1-2020 at 14:38


I recommend buying a condenser with a classic joint size like 24/40 and an adapter from your soxhlet to your condenser etc. That way you can use the condenser for other things too. I would also avoid a condenser without top joint (like the one you showed) as it cannot be connected at the top to other glassware if you need it.
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[*] posted on 1-2-2020 at 09:58


Thanks everyone. I'm planning to buy a new condenser soon :)

Quote: Originally posted by Texium (zts16)  
The only thing I use my Graham condenser for is when I distill bromine or diethyl ether. It works beautifully for those, but it's overkill for anything else that I've ever needed to distill. It's one of those pieces of glassware that if you're offered one for free, you should absolutely take it, but unless you're planning on setting up a large scale bromine still, you don't need to go out of your way to buy one.
So you claim that it's safe to use for extractions with ether? Because this is one of my main uses for the apertures.

My biggest concern was that due to the rapid boiling of ether - the condensed liquid might clog the condenser, resulting in a pressure buildup inside the apertures until eventually it would get high enough to squirt the ether out of the condenser into the surrounding area(e.g the hotplate).
Quote: Originally posted by Dr.Bob  
If you prefer an Allihn condenser for the Soxhlet, I have some extra conensers that fit most every size Soxhlet made. The Soxhlet's get broken way easier, so I have extra condensers. They are the best, short of a really big reflux one or a double condenser (jacket outside and coil inside), which I have a few of, but they are fragile and expensive. Note that using an adapter from 40/38 to 24/40 and a 24/40 condenser will almost certainly limit you a lot, as the condenser will just be too small to work well. There is a reason that most Soxhlets have larger diameter condensers on top, which is becasue they are needed to work well. Vapors need a lot of surface area to condense quickly.

The smaller diameter was a concern of mine too. But after some thinking I concluded that the larger diameter is probably there just to make it easier to get solids in and out of the extractor. And that no matter what the diameter of the condenser is, the bottle neck of the evaporation will most likely remain the narrow tube connecting between the bottom and the top of the apparatus.

[Edited on 2-2-2020 by B.D.E]
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[*] posted on 2-2-2020 at 08:14


Quote: Originally posted by B.D.E  
Thanks everyone. I'm planning to buy a new condenser soon :)

Quote: Originally posted by Texium (zts16)  
The only thing I use my Graham condenser for is when I distill bromine or diethyl ether. It works beautifully for those, but it's overkill for anything else that I've ever needed to distill. It's one of those pieces of glassware that if you're offered one for free, you should absolutely take it, but unless you're planning on setting up a large scale bromine still, you don't need to go out of your way to buy one.

So you claim that it's safe to use for extractions with ether?
Because this is one of my main uses for the apertures.


[Edited on 2-2-2020 by B.D.E]


I did not read the term extractions. Perhaps reread this thread carefully.
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XeonTheMGPony
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[*] posted on 2-2-2020 at 08:26


Grams are good for RECOVERING Ether by distillation or for making Bromine liquid.

For reflux based extraction Dimroth or Allihn.
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[*] posted on 2-2-2020 at 15:18


I think you have your answer already, but the Graham condenser is apt to start "gurgling" and will eventually start to spew out the top if left unchecked. It is a really poor design on their part...

Probably with some additional tubing, you could make it into a condenser for a water distiller or something :]




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[*] posted on 12-2-2020 at 05:49


Quote: Originally posted by XeonTheMGPony  
Grams are good for RECOVERING Ether by distillation or for making Bromine liquid.

For reflux based extraction Dimroth or Allihn.

Got you :)
Quote: Originally posted by Steam  
I think you have your answer already, but the Graham condenser is apt to start "gurgling" and will eventually start to spew out the top if left unchecked. It is a really poor design on their part...

Probably with some additional tubing, you could make it into a condenser for a water distiller or something :]

Thanks for the advice man.
I actually used it as a "suck-back trap" and it worked quite nice(the reaction on the other hand was a complete failure).


and yes I got my answer. thanks everyone :P
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