03-07-02 21:53
No 278512
Hey Everybody,
Bout ready to order a big ol' mess of glassware (all 24/40) and
am needing some advice here.
1) Allihn vs Graham vs Friedrich...which is more efficient at refluxing?
* 400mm Allihn stuffed with steel wool or
* 400mm Graham (the type Rhodium has where the cooling
water circulates INside the spiral jacket) or
* Friedrich of comparable size
(probably the Fried. but if its too $ I'll end up
going with one of the other two)
2) How does one professionally refer to the type of Graham Rhodium
speaks of where the cooling water circulates inside the coil
instead of the shitty Graham whose design allows the condensate
to form inside the glass coil? Don't want to sound like an idiot
over the phone you know!
3) Gonna go ahead and get a small Vigreux for better separations
when vac. frac. distilling. What size to get? 100mm?
4) This next one I'm just kind of sneaking in here...I've read it
somewhere here on the hive before, but I've forgotten what
the suggested length mentioned was.
What size Liebig of West for downward vac. frac. dist? 200mm?
250mm? 300mm? (again, 24/40 setup using 2-3L distn. flask)
Thanks in advance
Cheers!...a
circlesnort
(Hive Bee)
03-08-02 00:21
No 278584
i don't have much to contribute, other than stay the hell away from the shitty graham condensers. they are not worth it. they clog with condensate and require constant dilligence. if you choose to disagree, you can buy SWIMs for CHEAP!!!! (kidding, no commerce on the HIVE)
SWIM has a six bulb, 300mm allihn that has served SWIM well. it was cheap, and has been very sturdy and useful.
i learned a thing or two from charlie dontcha know.
(Hive Bee)
03-08-02 02:02
No 278648
The project blackbook posts says a 400mm Allihn is the one to use for a MM reflux, but probably overkill for a lot of others.
Pardon my friend officer, He's a little slow.
(Hive Addict)
03-08-02 02:36
No 278663
My recommendations?
Buy a reflux condenser. Use it for refluxing. You won't be disappointed.
Buy a liebig condenser. Use it for regular distilling. You won't be disappointed.
I'd recommend a 200mm Liebig, and a 200mm reflux condenser for most mid-scale bees. The reflux condenser can be stacked with the Liebig if you've doing a fast solvent distillation. It is an awesome sight.
(Daddy)
03-08-02 08:38
No 278802
Standard distillation setup drawing :
Fractional distillation setup drawing :
WISDOMwillWIN
(Old P2P Cook)
03-08-02 22:20
No 279063
(Rated as: excellent)
which is more efficient at refluxing?
* 400mm Allihn stuffed with steel wool or
You don't put packing in a condenser being used for reflux. Doing this will just reduce the capacity of the condenser. The only time that you put packing in a condenser is when it is being used as a fractionating column.
A Friedrich condenser is the best for holding back a heavy reflux. A Friedrich condenser should not be used under vacuum though so it is not suitable for use as the condenser in a vacuum distillation.
(Newbee)
03-09-02 04:12
No 279225
Seems like SWIMS seen those drawings somewhere else LaBTop... *cough Zubrick *cough
Swim uses a 400mm Leibig condenser for distillation and a 400mm Allihn condenser for refluxing, has always worked great for him. Although the one described by rhodium would be kick ass for refluxing. SWIM may just pick one of those up ;)
-OC
"We can't solve problems by using the same kind of thinking we used when we created them."
(Junior Service Representative)
03-09-02 04:53
No 279240
Is a 200mm Leibig long enough? What's the ideal length for 0.5L distillations, or less...?
PB
(Newbee)
03-09-02 08:50
No 279329
SWIM prefers a longer condenser. More surface area = Faster condensing. A 200mm Leibig should be sufficient, will just take longer to distill. SWIM has 5 or 6 and prefers his 400mm Leibig above all others for distilling. SWIM just needs a 20L Rotovap now
.-OC
"We can't solve problems by using the same kind of thinking we used when we created them."
(Hive Bee)
03-12-02 22:10
No 281415
RB: Yeah...Graham condensers (condensate in coil) have no real applications as far as most here are concerned.
SS: much oblidged
Chromic: much appreciated
LabTop: many thanks
Terbium: I thought I had read that stuffing a column with ss wool gives the solvent(g) more surface area on
which to condense into solvent(aq)...thus making for a more efficient condenser. To me it makes
sense that if wool helps in a frac. colmn. that it would also give additional help in keeping back
a vigorous reflux.
I'll definatly take your advice, though...thanks T.
oc: Yea...I've really been searching for the name of this type of reflux condenser but haven't found the
ans. yet. 'Inside-Out Graham' maybe?
Can anybody help name this type of reverse-Graham in which the circ. water runs INside the glass coil and the
condensate forms OUTside the coil and then drops back into the reflux flask? ...Rhodium? ...anybody?
Thanks Everybody for your help...off now to play some Q*Bert
Load"*",8,1
(Chief Bee)
03-12-02 22:33
No 281432
(Rated as: good read)
This is a Graham condenser, as we already know. 
This is called a 'coil condenser' by most suppliers. 
Finally, I have found an example of what Graham condensers are good for - it is a downward distillation condenser!
(Hive Bee)
03-12-02 23:39
No 281481
so, we're saying that coil condensers are useful?
i know that graham condensers are useless... i'm thinking of taking mine out and shooting it with my paper clips and rubber bands.
any other fun that could be had with it? turn it into a bong of some sort? i don't smoke, so that's not much use to me.
i learned a thing or two from charlie dontcha know.
(Newbee)
03-13-02 10:20
No 281881
>i know that graham condensers are useless... i'm thinking of taking mine out and shooting it with my paper clips and rubber bands.
Why? Now that Rhodium posted the picture of the condenser as a *downward* condenser, it actually seems like a pretty handy piece of glassware. I always thought they looked like a stupid design too, but with the proper adapter on the top you could reduce the surface area of your workstation while increasing the surface area of your condenser. That seems like an all-around win.
(Hive Bee)
03-21-02 07:09
No 285729
Wouldn't the coil condenser (where the vapour is forced through the coils) be effective in holding back a refluxing solution with a volitle gas component??
Take methylamine for instance... Say you were refluxing a reaction mixture that contained it or some other volitle component-- now, throw an Allihn on the flask and one of those "shitty" Graham condensers on top of it.. It might be more effective at holding back extremely volitile reaction mixtures..
Julia
(Chief Bee)
03-21-02 07:20
No 285733
You would have to pump freezer-cold antifreeze through it - methylamine boils at -6°C.