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Magpie
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[*] posted on 26-8-2004 at 08:15
condensers


I'm hoping this thread can be a general discussion of condensers. There are a great many condenser configurations and the inventors must have had something specific in mind when they conjured up their designs.

I have an old condenser given to me over forty years ago. It is in a CENCO box that says "Liegig's condenser." But I don't think it is a Liebig. It has an 8" long shell containing a 1/4" diameter helical inner (vapor) tube. Is this a Graham? What is it specifically designed for? Thanks for any help that you can give.




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Organikum
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[*] posted on 26-8-2004 at 09:10


Its a spiral condensor, useful for condensing volantile low-boiling compounds, from ethylalcohol to ethylether, DCM, benzene etc. Very effective cooling but rather high back-pressure - not so good for distillations with lots of BUMPING.
Absolutely not useful for reflux.




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[*] posted on 26-8-2004 at 09:37


Thanks, Organikum. That is helpful information.

The Vigreux and packed columns are used for fractional distillation, right? Which is the best for this, or does that depend on the application? What is the Vigreux specifically designed for?

The reflux condenser and the West condenser are similar but the reflux condenser is the shorter, fatter one, correct?




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[*] posted on 26-8-2004 at 09:44


Vigreux column is fast with high flow rate, but less efficient separation. The boiling ponts should atleast be 20C or more apart for a 30cm one.

A packed column is very efficient but has a very low flow rate.

In theory, you can use any condensor for reflux except the spiral condensor because this one will propell liquid out the top.
However, it's obvious that a liebig cooler is not very well suited for reflux because of laminar flow.




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[*] posted on 26-8-2004 at 10:00


Colums are something quite different than condensors - please dont mix things up.

A reflux condensor can be anything which represents no or almost no resistance to the gases, say the "free aperture for flow" has to be similar or bigger than the opening to the flask. Or it may be blown out or even destroyed. Happens quite often btw.

For the columns you may have a look into Vogel´s 3rd where this explained in detail, vultures explanaition was basically right though.
The Vigreux is the quick-shot for the lab, no good separation but easy to clean, and cheap. The Hempel - the tube filled with Raschig-rings or similar has a better separation but holds back lots of volume - not good for smaller amounts to distill, but perfect when time is not important and you process quantities of something. Also cheap and easy.
The "spinning band column" is the master, but thats not a cheapo in special when you go for higher temps and need a platinum or tantalum band. Uh.

And as we mixed already columns and condensors I cannot resist to throw in the fine "reactive distillation" - thats a good one! :D
Or the destructive distillation.
Or....

[Edited on 26-8-2004 by Organikum]




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[*] posted on 26-8-2004 at 13:45


Why would you need a graham condenser for distilling ethanol? I wouldn't use a graham condenser for anything which boils over 40 C, it's just redundant. Thus, out of the common applications I use it for dichloromethane, ether, and acetaldehyde. I have heard a little about using acetone/dry ice mixtures to condense gases such as methylamine and ammonia, but I don't know very much about this. As for reflux condensers, your standard inner coil, outer jacket are pretty nice. There are those with a larger coild for low vapor pressure solvents. Friedrich condensers are pretty nice and there was one on sale on ebay, ground glass, for $48.50. Then there is the king, Go to http://www.chemglass.com/index.htm and search for product number CG-1215-C.

[Edited on 26-8-2004 by Mendeleev]




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[*] posted on 26-8-2004 at 22:42
Graham


Magpie, that does sound like a Graham condenser. My Liebigs are
straight tubes. I have both in my collection. Picture enclosed. The
Grahams are on the top, the Liebigs are on the bottom. The Friedrich's
is just below the Graham's. Sorry, I need to get a better snapshot.
Look in the "whimsy" section under "Lab Photos". Can't seem
to find that goddam browse button again.

[Edited on 27-8-2004 by MadHatter]




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[*] posted on 27-8-2004 at 01:30
Picture


Magpie, sorry about the color. The condenser is actually clear.
Picture of my Friedrich's condenser:

FRIEDRICH.jpg - 146kB




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[*] posted on 27-8-2004 at 01:32


Isn't that a condensor for a rotavap? (asked the same question in whimsy, but it's more clear here)



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[*] posted on 27-8-2004 at 01:54
Condenser


Vulture, mon ami,you have the response time of a bolt of lightning !
The only thing I can tell you is that it's made by LabGlass out of
Vineland, New Jersey with a 24/40 joint on the sideneck. It looks
like a Friedrich's but I could be wrong. Maybe you know more about
it than I do. It really doesn't matter to me - it's another beautiful
piece of glass in my condenser collection ! It appears to be unused
but it sounds as though you know more about it than I do. I'd be
interested in any info you may have on it !




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[*] posted on 27-8-2004 at 01:59
Babylon....


Due to the wars the english and americans didnt love the germans anymore and started to rename pieces of glassware claiming it being own inventions. Like the siviets claimed that motorcars were invented by a certain "Ivan Automobilowitsch" ....


"Liebig" mutated to "West"
"Spiral" to "Graham"
etc .......

ORG


Oh, a "Intensiv" aka "high performance" - condensor with an outer water-jacket is a "Friedrichs" .
And the sameone without is a "Dimroth".
I think
;)
And yes the one with the outer jacket are used in Rotovaps.

There are all pics and more, reaction setups etc. on the ftp. Almost every information I have is on the ftp. Just look. You will be astonished although it takes some digging, but its worth the effort as I believe.



[Edited on 27-8-2004 by Organikum]




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[*] posted on 27-8-2004 at 02:17


here:

kühler.jpg - 25kB




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[*] posted on 27-8-2004 at 02:24


"Big Reaction" setup:

grosse_reaktion.jpg - 35kB




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[*] posted on 27-8-2004 at 03:24


Well, the cooler madhatter shows here is based on the intensive principle, but the dimensions have a different ratio than the normal lab ones, it's wider or shorter. The very wide ones with several connections (opposed to 2 for a lab one) are usually rotavap coolers.

Although the 24/40 joint doesn't point in that direction. Could you perhaps provide a picture with some sort of scale?

You might want to search on rotavaps, or rotating evaporators. A setup used to distill off solvents under vacuum using a bath wherein the flask rotates. This is a very clean and safe way of evaporating to dryness. Büchi is the leading company in this field.




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[*] posted on 27-8-2004 at 05:47


Rotovap:

rotovap.jpg - 46kB




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[*] posted on 27-8-2004 at 05:47


Well, as long as this thread is about condensors, I have a question. What do you use to condense vapors when distilling something with a bp? (Somewhere in the 250*C range.)
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[*] posted on 27-8-2004 at 06:17


250°C bp ?
A simple tube - aka "air-cooled condensor" suffices, or use a Liebig with warm water.

The temperature of solidification aka melting point (mp)) gets more interesting here. If your condenspr works to well you will clog it.
Then you may resort to "short way distillation"

kurzweg-feststoffdistill.jpg - 33kB




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[*] posted on 27-8-2004 at 07:10


Or the infamous "banana" cooler comes to mind. :D This would be a really good piece for madhatters collection.



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[*] posted on 27-8-2004 at 10:25


I'd heard about the simple air-cooling, but I didn't believe it because it doesn't sound like there would be much cooling going on, just air slowly moving by... Warm water!? Wouldn't that cause bumping in the condenser as it boiled? :o Also, doesn't the rule about the inside and outside of a glass vessel being less than 30*C apart also apply here?
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[*] posted on 27-8-2004 at 11:40


neutrino, you have so many misconceptions that its impossible to clear this up, sorry. Download the Vogel´s 3rd from the ftp or Rhodiums page and read the chapter on distillation please.

vulture, thats a "sabre" no "banana" ;)




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[*] posted on 27-8-2004 at 16:17


I have actually already read that chapter, there wasn't anything on condensors in it. Just bumping, vapor-pressure calculations, and the different types of distillation. Can you please elaborate on these misconceptions? I think there's some simple big thing I'm missing here...

:edit:
Wait... I think I know what you're thinking... I know that the liquid to be distilled doesn't boil in the condensor!:P What I was thinking was that the cooling water would heat up to about 30*C less than the distillate vapor (due to the 30*C rule), which would still be way over the boiling point of water, so the water would boil. Seeing as you probably couldn't pack a condensor with boiling stones, the water would probably boil irregularly in the jacket and thus constitute bumping. Now, judjung by your reply, the inner tube in a condenser can take more than a 30*C difference between the inner and outer walls?

[Edited on 28-8-2004 by neutrino]
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[*] posted on 28-8-2004 at 02:05


The water in the cooling jacket is - except for air-cooled condensors or Dewar-type condensors - circulated by a pump.
So what I wrote said - understandable to everybody but you, neutrino - that the condensor should be fed with warm water circulated by a pump.
The rule says that the difference between cooling water and the bp of distillate should be AT LEAST 30°C - not max.

That Vogel´s 3rd says nothing about condensors, isnt this embarrassing? Whatta fucker this Vogels idiot must have been to leave this out!
Unbelievable this is.
And not true.
At page 48 of Vogels 3rd are the different types of condensors depicted, on page 47 they are described and their uses named.

neutrino, you are walking thin ice. You are either not able to use the INDEX of a book and to look there for "condensor" what would speak of VERY limited intellectual capabilities, or you are fucking around with me, what I dont like (includes consequences of course). For sure you are EXTREMELY unpolite.

You now may choose: You change your behaviour and we forget this, or you go on and we forget you.
Make your choice!

ORG




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[*] posted on 28-8-2004 at 05:02


I knew about the circulation and such, I was just misinformed about the temperature gradient. In your first post, I thought you meant the distillation section specifically, and not the condensor section. That section also didn't mention the gradient, so I was lost. Thank you for clearing this up for me.

I say we just forget this little misunderstanding and go on with our lives.
P.S. How was I rude? I certainly wasn't trying to be. I'm sorry if I was.

[Edited on 28-8-2004 by neutrino]
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[*] posted on 28-8-2004 at 08:55


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).
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[*] posted on 28-8-2004 at 10:18


Ok, lets start over. (I never said you were "rude" btw. - "unpolite" is far less strong in my understanding)
Neutrino, what are you want to say with "distillation-section"? We were talking condensors - you and I - nothing else. Do you refer to whats happening in a column so attached? This would be called "rectification".
These two things should not get mixed up as I wrote before as this is a mayor point of confusion.

For your high-boiling substance you may use a short Vigreux-COLUMN (15cm) and then a condensor setup as told above. Any longer column will need good isolation, either a vacuum-jacket (preferred) or glasswool insulation and distillation will get slower.

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.




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