| Pages:
1
2
3
4 |
vulture
Forum Gatekeeper
Posts: 3330
Registered: 25-5-2002
Location: France
Member Is Offline
Mood: No Mood
|
|
| Quote: |
I looked at the condenser Madhatter posted, and it looks like it goes with a Soxhlet extraction setup. The large bottom joint plugs into the extractor
body's upper joint, avoiding the need for an adapter (i.e. if using an all-24/40 condenser with a 45/50 extractor).
|
I don't concur. The condensor has too many connections for this. I have such a soxhlet condensor myself and it simply is a jacketed reflux
condensor with one larger joint.
EDIT:
| Quote: |
PS: the "15cm" refers to the ACTIVE part of the column where actually rectification takes place, the grounded joints etc. dont count to the
length.
|
True, but rectification takes place on any vertical surface, just not that efficient because of laminar (or stagnant) flow.
[Edited on 28-8-2004 by vulture]
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
|
|
|
Organikum
resurrected
Posts: 2337
Registered: 12-10-2002
Location: Europe
Member Is Offline
Mood: frustrated
|
|
If the compound you are thinking on is something with properties like safrole you cannot distill thus without decomposition, you need a strong
vacuum-pump for this. This is true for many of the natural oils.
You can "freeze out" safrole though. (and many other natural oils).
Other oily substances like phenyl-2-propanone as an example are better steam-distilled as they are quite well volantile with steam (an external
steamsource is preferred). This substance for example can be distilled at STP (standard-pressure, no vac-pump) with only minor decomposition taking
place, but I would recommend to steam-distill first and tu use direct distillation if the steam doesnt suffice to produce a clean enough product for
further experimentation.
There exist some rules of thumb in distillation and a thousand exceptions in realworld. Its a mess. 
|
|
|
Senjoro Nie
Harmless
Posts: 3
Registered: 3-8-2004
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by vulture
I don't concur. The condensor has too many connections for this. I have such a soxhlet condensor myself and it simply is a jacketed reflux
condensor with one larger joint.
|
My Soxhlet apparatus came with a Friedrichs-type condenser like the one in Madhatter's picture.  Alas it is now broken, so I use an all-24/40 Friedrichs with a size adapter instead.
Most Soxhlet condensers are what you described, usually an Allihn-type condenser. Madhatter's is a Friedrichs-type -- instead of an outer
cooling jacket, there is instead a coolant-filled cold finger surrounded by a glass outer wall. That's why the connections look so odd. The
topmost hose barb is the coolant inlet, and the side hose barb is the coolant return. The ST joint on the side mainly serves as the vent, though it
can accept a ST drying tube (keeps condensation out) or it can be used as a distillation inlet. The oversize bottom ST joint (34/45?) more or less
gives it away as being intended for a Soxhlet apparatus, but certainly it could be used for reflux in a large flask.
Personally, I prefer the Friedrichs-types because the cold finger is protected from the air by the condenser's outer wall, so the coolant absorbs
less heat from ambient air. I use an ice bath and pump, so it means I have to use less ice. Plus, the spirals on the cold finger and the narrow
space between it and the outer wall gives very good condensing efficiency, useful for those low-boiling solvents.
The downside is that the top hose barb is extremely prone to being broken off by accident. Not good, especially considering that Friedrichs
condensers cost a good bit more than the more common Allihn or Liebig types!
EDIT: Here's one from Fisher's website: https://www1.fishersci.com/Coupon?cid=1328&gid=145730&am...
[Edited on 30-8-2004 by Senjoro Nie]
|
|
|
Mendeleev
Hazard to Others
Posts: 237
Registered: 25-12-2003
Location: USA
Member Is Offline
Mood: stoned
|
|
When distilling a low bp liquid like ether or DCM, and using a graham condenser, does the graham condenser have to be in a vertical position? It
looks as if the liquid, once condensed, would accumulate in the dips in the spiral if it was held like a standard setup using a liebig condenser at a
slight angle.
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
|
|
|
vulture
Forum Gatekeeper
Posts: 3330
Registered: 25-5-2002
Location: France
Member Is Offline
Mood: No Mood
|
|
Yes, it has to be vertical. Also, never use it for reflux, unless you want liquid shooting out at the top.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
|
|
|
Mendeleev
Hazard to Others
Posts: 237
Registered: 25-12-2003
Location: USA
Member Is Offline
Mood: stoned
|
|
So is there any real necessity in a graham condenser for things such as ether or DCM? I mean if you can get ice water to circulate through a 400 mm
liebig or a 300 mm allihn then there shouldn't really be a need for it in these applications. I doubt it will improve efficiency that much.
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
|
|
|
Organikum
resurrected
Posts: 2337
Registered: 12-10-2002
Location: Europe
Member Is Offline
Mood: frustrated
|
|
If you dont overdo the heating and distill slowly in special with a column an ice-water cooled long Liebig suffices. A copper made Liebig is very good
for low-boiling solvents, but one of glass will work too.
/ORG
|
|
|
Quince
National Hazard
Posts: 773
Registered: 31-1-2005
Location: Vancouver, BC
Member Is Offline
Mood: No Mood
|
|
I've got three questions for this thread.
Why is it a problem if distillate collects in the dips of a tilted Graham condenser? Wouldn't pressure buildup push the liquid plugs through,
and any remaining be drained by standing it upright at the end of distillation? This would be even more effective if vacuum is used. I'm asking
as I have one on the way, and I'd not be happy to have to get a second condenser (I was trying to go for a minimalistic setup).
My next question: I still don't understand how Dewar condensers work.
Finally, I can't figure out how the solvent recovery condenser at the bottom of http://www.uicoglass.com/condensers.htm works.
Thanks in advance for answers.
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
|
|
|
neutrino
International Hazard
Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline
Mood: oscillating
|
|
Dewars are simple: the vapor is introduced at the side, condenses on the cool inner part (in which the cooling mix is sitting, but on the outside of
the condenser), and drips out the bottom.
|
|
|
HNO3
Hazard to Others
Posts: 211
Registered: 10-11-2004
Location: America
Member Is Offline
Mood: No Mood
|
|
The solvent recovery condenser is what you put on a RBF after your soxlet extraction is performed. The solvent condenses and runs to the bottom of the
condenser, where it is removed through the stopcock controlled opening.
|
|
|
Quince
National Hazard
Posts: 773
Registered: 31-1-2005
Location: Vancouver, BC
Member Is Offline
Mood: No Mood
|
|
Thanks. So only my tilted Graham condenser question remains. (I only have angled attachments, and no money now for more glassware.)
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
|
|
|
Quince
National Hazard
Posts: 773
Registered: 31-1-2005
Location: Vancouver, BC
Member Is Offline
Mood: No Mood
|
|
Anyone? I'm stuck with the Graham for now. I was thinking I could make a U turn with the two angle adapters, and have the Graham vertical over
the collecting flask, but the problem is that I only have the two adapters, one of which has the protrusion for attaching the vacuum hose, and that of
course has to be on the collecting side. So I guess I'm screwed, unless I find a third straight adapter with a vacuum connector, or maybe I can
sort of tilt the whole setup 45* so the condenser's about vertical, and use less liquid volume in the boiling flask so it doesn't reach the
throat.
Also, is aquarium air tubing strong enough for vacuum? I ask as I can get it very cheap, and if it were to corrode from HNO3 I wouldn't care as
it costs little to replace. What about silicone tubing as used in glow fuel lines for RC models? I also have a bunch of PTFE Teflon tubing but the
stupid thing is barely flexible and creases when I try to bend it.
[Edited on 24-2-2005 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
|
|
|
mick
Hazard to Others
Posts: 338
Registered: 3-10-2003
Member Is Offline
Mood: No Mood
|
|
The dewar condenser can also be used with salt + ice mixture etc.
The standard cold temp stuff is dri-ice + actone or iso-propanol at -78oC and then slush baths with liguid nitrogen. Reactions are carried out at
-78oC because that is the easy option but they might work at -50oC or some thing. My own home freezer is on the way out, no temp. control and it makes
a funny noise when it cuts out but the temp. gauge reads below -40oC and it is cold. I have seen -55oC refidgeration boxes and even -104oC boxes.
Polyetheylene is good at low temp. and fairly solvent resistant, polyproylene is good but not as good.
A quick question, what would be the best thing to put in some small sealed containers that could be recycled with freezing down to -40 or 50oC and be
able to cool down a cooling bath to that temp (used as low temp recyclable ice cubes??). I have been thinking of a low molecular wt polyethylene
glycol.
Back to Quince's question, silcone tubing seems to be very chemical resistant but soft and might collapse under vacuum unless heavy walled, or
feed it through a bit of stronger tubing of slightly larger diameter and that should stop it collapsing.
For good filtration under vac. you need to pull the liquid through the filter and collect the solid, low vacuum will do this. If you use high vacuum,
the liquid will evaporate in the filter and block it up (the more vacuum, the more blocked up filter you might have). A good way to do vacuum
filtration, especially with volatile solvents, is to put the vac. on and then close the vac line and when it stops filtering put a bit more vac on it.
mick
To bend PTFE, if you warm it up to around 200oC you can usually get a long bend in the tubing, cool under water. If the PTFE goes clear then it will
probably collapse. If you start smelling anything then you might have HF so be careful.
mick
[Edited on 24-2-2005 by mick]
|
|
|
Quince
National Hazard
Posts: 773
Registered: 31-1-2005
Location: Vancouver, BC
Member Is Offline
Mood: No Mood
|
|
Can I assume my Graham condenser will withstand vacuum from an aspirator? I'd hate to find out otherwise the hard way...
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
|
|
|
MadHatter
International Hazard
Posts: 1340
Registered: 9-7-2004
Location: Maine
Member Is Offline
Mood: Enjoying retirement
|
|
HNO3
Quince, I can't answer your question about vacuum for a graham condenser as I've
never used any of mine in that type of application. I've always used liebigs.
As for plastics that will stand up to HNO3, a quick google revealed that Kel-F, Kynar,
Teflon, and Viton have excellent resistance.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
|
|
|
UhhKaipShaltaBlet
Harmless
Posts: 11
Registered: 23-1-2005
Member Is Offline
Mood: Shalta Blet ...
|
|
OK, I have question. Is Graham condenser suitable for HNO3 distillation ? I think Condensed(Sp?) HNO3 Vapour will drip into lowest "ring"
point. Or it will be pushed by another gas portion coming ? I think if vacuum used it will suck that distillate wich can get up. Or I Should use
Liebig condenser ? Here is the pics of Graham.
http://img.photobucket.com/albums/v281/formyfaFire2/PICT0023...
http://img.photobucket.com/albums/v281/formyfaFire2/PICT0022...
http://img.photobucket.com/albums/v281/formyfaFire2/PICT0021...
|
|
|
Dave Angel
Hazard to Others
Posts: 128
Registered: 22-3-2005
Location: UK
Member Is Offline
Mood: 0 K
|
|
Just a few remarks on nomenclature here:
Is the Graham type condenser not that which has the coil carrying the coolant? A google image search gives mixed results in that both coolant coil and
vapour coil are given as Graham types. My glassware catalogue would seem to indicate that the latter (or a very similar condenser with a vapour-coil
anyway) is actually known as an Inland Revenue (!) condenser; must be a UK thing. 
As for your situation UKSB; I'd go with the Liebig and vacuum - that should be fine. In fact, you'd be okay without the vacuum for HNO3,
though you may find you'll need to purge it of nitrogen oxides if you want white nitric. My thinking about the vapour-coil pattern condenser is
that if one did not have it vertical, there would be welling of condensate in each dip.
|
|
|
neutrino
International Hazard
Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline
Mood: oscillating
|
|
I’ve always seen a graham as the kind with vapor going through the coil. If you save coolant going through the coil, you have a reflux condenser.
|
|
|
Dave Angel
Hazard to Others
Posts: 128
Registered: 22-3-2005
Location: UK
Member Is Offline
Mood: 0 K
|
|
Perhaps it is a UK thing, and Grahams over here are coolant-coil, whilst yours are vapour-coil:
UK
USA
|
|
|
MadHatter
International Hazard
Posts: 1340
Registered: 9-7-2004
Location: Maine
Member Is Offline
Mood: Enjoying retirement
|
|
Coil condensers
I have both types of condensers in my collection. The condensate does form in the
coils of a Graham. My Dimroth condenser, as identified by Vulture, has the coolant
flowing through the coils and is a reflux condenser.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
|
|
|
Dave Angel
Hazard to Others
Posts: 128
Registered: 22-3-2005
Location: UK
Member Is Offline
Mood: 0 K
|
|
Sō-nano? ^^
Equally, I could state that it is coolant that flows through the coils of a Graham as I own a Graham as per catalogue and quickfit code - but
that does not make either of us internationally correct! 
If I write about using one in any procedure I will be sure to make my description suitably... descriptive. 
|
|
|
MadHatter
International Hazard
Posts: 1340
Registered: 9-7-2004
Location: Maine
Member Is Offline
Mood: Enjoying retirement
|
|
Coils
Good point ! I look at it from what is probably standard lab method of use but there's
nothing saying it couldn't be adapted to work differently based on the application.
I've used inverted flasks to act as reflux condensers to make booze. This is of course
before I got my stills.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
|
|
|
Quince
National Hazard
Posts: 773
Registered: 31-1-2005
Location: Vancouver, BC
Member Is Offline
Mood: No Mood
|
|
Someone mentioned Liebig vs West condensers above. This is not just a regional naming difference, they are actually different. As opposed to the
Liebig, the West has a wide inner channel and narrowed outer jacket, forcing a high flow rate and surface area of the coolant.
BTW, does using a Vigreux column help separation when distilling ethanol from say, wine? How do I figure out the proper amount of insulation to put
around a Vigreux, i.e., what's the correct temperature distribution along the column?
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
|
|
|
The_Davster
A pnictogen
Posts: 2861
Registered: 18-11-2003
Member Is Offline
Mood: .
|
|
Many of you have mentioned in other threads that you use pond pumps to run cold water through your condenser. I bought a 68 GPH fountain pump and it
does not put nearly enough water through my 20cm 19/22 leibig. What would everyone recomend in terms of GPH or LPH that would work well for my
condensor?
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Don't know what to say. Mine is a 60 gph Beckett rated for a foot of lift, 40 gph @ 2'. Works fine on 400 mm Liebigs, with the pump at the
same level as the receiver, the receiver is usually in the recirculating tank. Works the same with ice or steaming hot water. They don't come any
cheaper than this one, AFAIK.
It has never liked being taken out of water after being shut off, though. It has to be smacked or vacuum applied to the other end of the condenser to
get the air out, but then runs fine after the air in the pump gets out. So I keep it in a glass of water when off to prevent this, if I remember to do
so.
|
|
|
| Pages:
1
2
3
4 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
