Say I was to have a liebig condenser, for my distillations, and an Allihn condenser, for refluxing.
If I already had these two condensers, would a graham condenser be basically useless??
I really can't come up with any scenario in which using a graham would be better than using an allihn or a liebig.Mailinmypocket - 13-11-2015 at 12:13
They are good for condensing things with very low boiling points because of their long spiral path through the cooling jacket. They need to be run
vertically though. I almost never use mine unless it's to recycle solvents or things like that. They also can't really be used for refluxing either.Upsilon - 13-11-2015 at 12:30
Not necessarily, they can be run the same way as a Liebig because the pressure of the incoming gas forces any condensed liquid on through the coils.
Some product will be lost in the low points of the coils but it's not really a big deal, blow some gas through it if you really want that small
amount.Mailinmypocket - 13-11-2015 at 12:48
Well no, not necessarily but it isn't really the best situation. I've never seen a graham used in such a way in labs I have worked in. It also could
cause unwanted pressure in the vessel and make boiling points fluctuate although probably not severely. ParadoxChem126 - 13-11-2015 at 13:10
I've attempted to use Graham condensers in the horizontal configuration, but it is extremely frustrating. Like Mailinmypocket said, it results in a
pressure buildup which causes bumping issues and fluctuations in boiling point. Additionally, all of the liquid within the coils is liable to
suck-back when the temperature drops. In one case, I had a good 20 mL of my product get sucked back into the still pot after a two hour distillation.
Frustrating... To say the least.
cyanureeves - 13-11-2015 at 17:39
my allihn worked great as a condenser but also had to be used vertically and so i had to set the boiling flask and hot plate up on a cinder block.Texium - 13-11-2015 at 18:10
Every condenser has its place, but if you can only have one condenser, a good ol' Liebig can't be beat. I have a few different condensers, and I
usually use my Liebig for distillation and my Friedrich's for reflux. I've only used my Graham twice: once for ether and once for bromine, in a
vertical configuration both times. It worked great in both of those situations, but it hasn't seen any other use.
[Edited on 11-14-2015 by zts16]JJay - 13-11-2015 at 18:44
I have a pretty limited selection of lab equipment here, so I have only one condensor, a Liebig. I usually use a Dimroth condenser for reflux, but I
used my Liebig yesterday and was surprised at how efficiently it condensed.jamit - 13-11-2015 at 19:18
I have all the bells and whistles when it comes to condensers. For most home lab use, the liebig can't be beat! I've used the graham condenser just
once, vertically for ether.Sniffity - 14-11-2015 at 06:23
So; if I'm going to use a graham condenser.. I'll need to find an adapter that will make it usable vertically. Any ideas as to what the name of this
adapter might be?? Sulaiman - 14-11-2015 at 06:45
It's good to have a parallel adapter anyway, as you can also use it as an air cooled condenser or drape a cold pack over it to make a more efficient
condenser. I use that sometimes when I'm feeling too lazy to set up the water pump and everything.Sniffity - 14-11-2015 at 21:17
Two more questions:
What about using a three way adapter, joined to a 105 degree adapter, joined to the graham? (The one that usually goes at the end of the condenser,
but without the vacuum take off). Would that work?
Also, a last question. If using a Liebig condenser, in a semihorizontal position for distillation, I'd usually fit an adapter with a vacuum take off
at the end, leading to a flask and a potential vacuum source. Say I'm not doing a vacuum distillation... Can I use an adapter without the vacuum take
off? The same one I'm referring to above? I always see people using a vacuum take off adapter, even if they're not pulling a vacuum. Why is this? Why
not use an adapter without a vacuum take off if you're not pulling a vacuum through the system? One like this: http://m.ebay.co.uk/itm/270382199291?_mwBanner=1Texium - 14-11-2015 at 21:22
If you don't use a vacuum take-off whether you're pulling a vacuum or not, the apparatus will build up pressure and come apart. It seems obvious once
you think about it. I learned the hard way the first time I did a distillation.
Edit: And if you're using a Graham condenser with a ground glass joint at the bottom, you'll want to put a vertical vacuum take-off at the end of it,
or at least leave the joint open slightly.
[Edited on 11-15-2015 by zts16]Sniffity - 14-11-2015 at 22:33
!!!
Okay, that seems pretty obvious now. Didn't stop to think of that. Glad I didn't actually try doing it .
As for the Graham Condenser..
It's clear, as you pointed out, that I need some source for releasing the pressure. I'll asume this pressure venting will have to be post
condesnation, as doing it pre-condensation would lead to loss of valuable uncondensed vapours, correct?
Finally: As for the actual connection of the graham to the rest of the apparatus: Is the parallel adapter strictly necessary?
How about : Three way adapter goes into 105 degree adapter (same angle as vacuum take off) goes into graham condenser, goes into receiving flask?s
Or would this provide too little space between the boiling flask and the condenser?
Thanks!
Ps: @zts16 Thanks alot for taking all this time to answer this small questions... It's these tiny details that you just can't find the answers to on
the internet, and only find them in experienced experimenters. Much appreciated!j_sum1 - 14-11-2015 at 22:50
Agreed, Sniffity. the best place for this kind of information I have found is YT vids. Often you don't really know the questions to ask, but when
you see it, or in a good video, the experimenter comments on it, then you learn stuff that you would not want to learn the hard way.
NileRed, Nurdrage, Doug'sLab and MrHomeScientist are all favourites and offer good clear explanations.Texium - 14-11-2015 at 23:01
It's clear, as you pointed out, that I need some source for releasing the pressure. I'll asume this pressure venting will have to be post
condesnation, as doing it pre-condensation would lead to loss of valuable uncondensed vapours, correct?
Yep, you'll want it after the condenser. If it's something that isn't too volatile or nasty, leaving a small gap between the flask and the condenser
will be fine. If not, you might want to look into getting a vertical vacuum take-off.
Finally: As for the actual connection of the graham to the rest of the apparatus: Is the parallel adapter strictly necessary?
How about : Three way adapter goes into 105 degree adapter (same angle as vacuum take off) goes into graham condenser, goes into receiving flask?s
Or would this provide too little space between the boiling flask and the condenser?
Yes, that should work
just fine. You may have to tilt the boiling flask a bit to ensure that the condenser is vertical since the two sides will be at slightly different
angles, but that shouldn't be a problem.
Ps: @zts16 Thanks alot for taking all this time to answer this small questions... It's these tiny details that you just can't find the answers to on
the internet, and only find them in experienced experimenters. Much appreciated!
Sure, it's no problem! I
like to help out where I can, and I absolutely love glassware, so I'm glad that I'm able to help you out.JJay - 15-11-2015 at 00:22
Agreed, Sniffity. the best place for this kind of information I have found is YT vids. Often you don't really know the questions to ask, but when
you see it, or in a good video, the experimenter comments on it, then you learn stuff that you would not want to learn the hard way.
NileRed, Nurdrage, Doug'sLab and MrHomeScientist are all favourites and offer good clear explanations.
Chem Player is good too.byko3y - 15-11-2015 at 15:09
Only few chemists on youtube are experienced enough to show a really good setup. Anyway I would recommend you to try any crazy idea that comes to your
mind, brake some amount of glass and waste some amount of reagents in your failed attempts. There's no way you can learn without maing mistakes, until
you don't want to learn anything.
There are books describing some really good practical methods, like salt bath and salt bath, but nobody has exactly the same equipment and usually you
are forced to improvise, until you actually use exactly the same equipment.
