Cow Receivers for Fractional Distillation

[TheBlindGenius]

Does anybee here use these things?  Do you think they are worth the extra cash?  They look pretty handy, you don't have to change the flask (with all the things that come along with it) during a vacuum fractional distillation, you just turn the thing a little bit and the stuff falls into another one of three or four flasks.  Are they worth the $120+?  Take into account that is TBG's weekly paycheck.  Swim guesses you could use Keck clips to secure the three or four flasks.

[Rhodium]

They are indispensible for fractional vacuum distillation.

[Chicken]

How does this cow reciever differ for fractional distillation from a kugelrhor.  The kr has alwasy proved reliable for fracional dist for me.

[noj]

What's the trick to use this cow receiver? If you go from one flask to the one on the other extreme, everything will dump back into the current flask. Is this just a design flaw?

I see different ones that rotate horizontally, which I wish I would have purchased instead.
there's a big difference between criticizing your government and criticizing your country

[Rhodium]

Chicken: A kugelrohr apparatus costs $2000+ while a standard fractional distillation setup with a cow reciever costs $200.

Noj: You are supposed to orient the cow downwards:

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000360482-file_pjzu.jpg" title="View this image">

[Chicken]

What about a KR setup like this?
https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000360482-file_lryu.gif" title="View this image">
Very inexpensive.

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000360482-file_yaia.gif" title="View this image">
KR Bulb

Entire setup less then $200.

[Rhodium]

The glass maybe, but you still need the expensive kugelrohr oven, you cannot distill anything in that kind of glass vertically.

[ClearLight]

KR requires an air bath and optional cooling....

 Having seen the good Dr's  windshield wiper turner, with a cut down coffe urn heating element, i realized that good KR results could be had for $10.00 at a garage sale, plus a visit to a junkyard..

Infinite Radiant Light - THKRA

[Rhodium]

The good Dr uses ghetto equipment? Cool  

Could you describe the apparatus more in detail?

[terbium]

The good Dr uses ghetto equipment?
Aldrich, back in the days when the name was still unhyphenated and they would sell to most anyone who could put a money order in the mail, sold an inexpensive kugelrohr setup.

Kugelrohrs are great for quick cleaning a small amount of material but if you want to distill several hundred ml or more you should use a more usual distilling rig.

Post 181544

(terbium: "Re: Kugelrohr distillation.", Methods Discourse)

Post 182306

(terbium: "Re: Kugelrohr distillation.", Methods Discourse)

[Rhodium]

I know, it would just be so perfect for those really high-boiling things, which doesn't recrystallize.

Aldrich only sells their $2500 setup nowadays, and there are no cheaper things to find anywhere using google.

[TheBlindGenius]

to distill ketone, except probably it would need a distillation column between the distilling flask and the short path still body.

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000360482-file_geqy.jpg" title="View this image">

or maybe this?  probably they would work about the same?  or not?

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000360482-file_46i2.jpg" title="View this image">

But it seems that the cow receivers are mainly used in small scale distillations, like maybe 250 mL or less?  Anything more than that and the receiving flasks would be so heavy that the cow could break, right?  Then one would instead have to use a "real" distilling head with multiple stopcocks, two condensers, etc. (~$500) in order to continue distilling without disturbing the vacuum in the system.

[Rhodium]

Exactly like you described.

[noj]

Rhodium: yea, I realize this. But this particular model appears fine, but in reality, the first flask will dump when set for the third flask to ... you know what Im saying.
https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000360482-file_m1g2.gif" title="View this image">
there's a big difference between criticizing your government and criticizing your country

[Rhodium]

You aren't supposed to fill them more than 1/2-2/3 full, and not tilt it more than ~45°C in either direction.

[hCiLdOdUeDn]

i found a video for you guys....

http://www.chem.cuhk.edu.hk/labtech/Videoclip250/VACUUM_DISTILLATION.wvx

To bee or not to bee, that IS the question.

[Atropos]

A large coffee dispenser (you know, the old aluminum sided ones, about 2 1/2feet tall, with a heating coil attached to a variac, and covered with a crockpot lid... Figure out the temps with a thermometer.  In the side cut a hole for the neck of a large RBF, inserted from the inside of course.

The RBF is attached to a second dual necked spherical piece of glassware (like the bulb on a rotovap) that partially rests in a small trey filled with dry ice and acetone, or Sat NaCl and ice, with another straight glass tube attached to the vacuum with a flexible rubber hose that leads to a chilled condensor and then the vacuum pump.

You can actually have several of the bulbs attached for very volatile constituents.

The whole glass contraption is attached to a windshield wiper motor with a control spliced in to vary the rocking speed...

[Rhodium]

Atropos: I am not familiar with the coffee dispenser you are talking about - could you link a picture?

What kind of distillation temperatures could be expected from such a setup?


BTW, the above animation now also hosted here:

https://www.thevespiary.org/rhodium/Rhodium/archive/vacuum.distillation.wmv

[Osmium]

I've used such cow receivers to distill more than 1 liter quantities, and I've filled the receiving flasks (e.g. 1*500ml, 2*250ml for the main fraction and a 100ml for forerun) up to the top. I always use them, and I have yet a flask to drop or fall off.
Don't use those worthless Keck plastic clamps. They suck.
I'm not fat just horizontally disproportionate.

[GOD]

Then what would swiy recommend bee used?