09-25-02 22:28
No 360482
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.
(Chief Bee)
09-26-02 00:01
No 360500
They are indispensible for fractional vacuum distillation.
(Newbee)
09-26-02 00:35
No 360508
How does this cow reciever differ for fractional distillation from a kugelrhor. The kr has alwasy proved reliable for fracional dist for me.
(Hive Addict)
09-26-02 00:45
No 360511
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
(Chief Bee)
09-26-02 01:09
No 360523
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:
(Newbee)
09-26-02 01:16
No 360527
What about a KR setup like this?
Very inexpensive.
KR Bulb
Entire setup less then $200.
(Chief Bee)
09-26-02 01:20
No 360530
The glass maybe, but you still need the expensive kugelrohr oven, you cannot distill anything in that kind of glass vertically.
(Hive Addict)
09-26-02 01:24
No 360532
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
(Chief Bee)
09-26-02 02:27
No 360557
The good Dr uses ghetto equipment? Cool
Could you describe the apparatus more in detail?
(Old P2P Cook)
09-26-02 03:28
No 360574
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)
(Chief Bee)
09-26-02 03:36
No 360581
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.
(Hive Bee)
09-26-02 03:58
No 360593
to distill ketone, except probably it would need a distillation column between the distilling flask and the short path still body.
or maybe this? probably they would work about the same? or not?
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.
(Chief Bee)
09-26-02 04:20
No 360601
Exactly like you described.
(Hive Addict)
09-26-02 04:49
No 360616
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.
there's a big difference between criticizing your government and criticizing your country
(Chief Bee)
09-26-02 05:07
No 360627
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.
(Hive Bee)
09-26-02 05:15
No 360630
i found a video for you guys....
http://www.chem.cuhk.edu.hk/labtech/Vide
To bee or not to bee, that IS the question.
(Stranger / Eraser)
09-26-02 07:00
No 360656
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...
(Chief Bee)
09-26-02 07:03
No 360657
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: ../rhodium/archive/vacuum.di
(Stoni's sexual toy)
09-26-02 14:38
No 360736
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.
(Hive Addict)
09-26-02 15:03
No 360741
Then what would swiy recommend bee used?
(Hive Addict)
09-26-02 15:21
No 360745
Use glass that have the hooks for the metal springs. Although in experience, you will spend alot of time chasing those suckers if your fine motor skills are hampered by large hands.
there's a big difference between criticizing your government and criticizing your country
(Stoni's sexual toy)
09-26-02 16:14
No 360755
I exclusively use metal clips. Not the one resembling keck clips, they look different and will hold the glass together with considerable force (supplied by a spring). They could even be used for reactions under pressure.
These thingies will last for years and are unbreakable since they are made from stainless steel. I've yet to come across a pic of them online and I don't have a working camera around, so no pics unfortunately.
I'm not fat just horizontally disproportionate.
(Hive Addict)
09-26-02 17:27
No 360780
any ideas/suggestions for the poor ghetto dreamer?
(Chief Bee)
09-26-02 17:33
No 360784
For the clips? Buy them, they aren't expensive.
(Hive Bee)
09-26-02 18:09
No 360804
are a little expensive, maybe $120+ each, and are hard to come by in the used market. Try to get 2 just in case one breaks. These cows are very delicate because of their irregular shape. There isn't really any good way to ghetto-rig one that swim can think of. Swiy should just sell some product, a gram will buy swiy a brand new cow!
(Stranger / Eraser)
09-26-02 23:54
No 360936
Hmmm... I can't find a picture... Let me look a little more... Basically, it's a metal cylinder about 12" across, 1 1/2 feet high, and insulated inside to retain heat... Tight fitting lid... Anything similar will do...
I just gutted it an made the adjustments I mentioned...
Then just take a heating coil, and attached it to a variac, and put it inside through where the spigot was... It can get well over 250 degrees Celsius, and the outside stays *fairly* cool...
(Newbee)
09-26-02 23:59
No 360937
1. Cover
2. Coffee Basket
3. Stem
4. Heating Unit Well
5. Serving Spout
6. Ready Light
(Stranger)
09-27-02 00:09
No 360940
This type of cow won't allow the contents of the flasks to spill when the unit is rotated. The cow sits off a 105 degree vacuum takeoff which has a longer, bent tube which allows the distillate to fall into each receiving flask:
(Hive Addict)
09-27-02 21:45
No 361331
It looks like the one chicken posted, here's a link to the exact make..
http://www.comforthouse.com/comfort/12cu
It was cut down just below the handles, and had the coil unwound and lifted up. Apparently there's a built in thermostat, I didn't see a variac around it. No cooling was used, ran primary bulb into the heating chamber, 2 secondaries and a take off. The w/washer was a 2.5" dia motor 4" long that moved an arm up and down, which then rotated the bulbs.
I thought of several improvements, a teflon bushing in the slot on the urn would be a good idea for turning. A hair dryer or hot air gun would probably be more effective/efficient for heating things up. The pump went through a dry ice trap... "Neccessary for good vaccuum" was the quote...
He had remarked earlier that this was how he got those 5ml quantities of final product to distill to water white oils in the book...
It was quite impressive!
Infinite Radiant Light - THKRA
(Stoni's sexual toy)
09-27-02 21:51
No 361337
The Kugelrohr is very well suited to distill high-boiling stuff, compounds with a high molecular weight, tars and maybe even solids, but it will produce only poor separation efficiency. You can't successfully separate ketone and isosafrole, to give an example. Both will distill together.
I'm not fat just horizontally disproportionate.
(Hive Bee)
10-07-02 07:12
No 365337
Axatax, I just bought that exact model you got in the picture there. It's really nice. It cost me a little over $300, however, what sucks about it is that the biggest size they make it in, 24/40, which is the one I got, can only fit four 50 mL flasks on it, so maybe you could distill a maximum of 50 or 55 mL. I don't know, I was thinking i could use two or three of the flasks to collect that yellowish-green oil I love so much (lime extract of course
) and the other one or two to collect everything else, and that way be able to distill larger quantities. Not that I even have large quantities to distill (yet)