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amberdonut
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[*] posted on 18-2-2008 at 02:43
rotary vacuum distiller


Is it even possible to find one without it costing an arm and a leg these days? If so, where is a good place to look because I can't find any cheap sets, even used and/or refurbished!!
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[*] posted on 18-2-2008 at 08:27


University surplus? I bought one at surplus a few years ago, substantially complete, for US$60-70 -- and then sold it on eBay for around $200. :mad:
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[*] posted on 18-2-2008 at 17:14


I'm afraid those days are gone.

It used to be possible to find the old Model R Buchi w/plain stand or jackstand and water bath, and the basic diagonal condener setup for a few hundred dollars, at one time I had about 14 Buchis of various models. Now I have a few stands, some spare parts, and two working units, an R-110 with vertical condenser and a R-152 (industrial size, 20 liter) with E-type glass. The larger unit is an order of magnitude more costly.

Buchi glassware is expsnsive.

Used units go for $1000 and up, and often are close to retail and therefore a bad value.

"refurbished" is a joke. It is a word used by crooked dealers to describe a used piece of junk they maybe wiped the dust off of, if you are lucky. If the motor runs, the bath heats, and the glass is intact, there's nothing to refurbish, except the vacuum seal which needs periodic replacement by user anyway. How often depends on what you are rotavapping.

Some advice: the trick about using a Buchi efficiently is to run your bath at 60 C, not higher, and to adjust your vacuum so that the bp of your solvent that you are stripping is 40 C. For low boiling solvents, a bath is not required.

The condenser coolant needs to be 20 C or less. Use a recirculating chiller unless you live in a cold climate.

This is Buchi's 20/40/60 Rule for coolant/solvent/water bath as explained in manual for the V-805 vacuum controller. Which by the way is another couple thousand dollars.




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MagicJigPipe
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[*] posted on 19-2-2008 at 00:34


Speaking of recirculating chillers. Lately, I've been thinking of making one possibly out of a refridgerator condenser and some copper tubing (these are just thoughts now). A while back I did a quick search and determined that new ones seem to be way too expensive for what they are.

I used to work in an optical lab. We used one to cool the coolant water for the grinders and polishers used to "finish" the newly cut lens. It also cooled the polishing compound (aluminum oxide slurry) and the water for the "generator" (not an electricity generator. It's a machine used to cut a rough curve combination in a blank lens). I can't remember what temperature was needed but it did keep the water relatively cool even with all machines running at once.

Maybe I will visit some local optical labs to see if they are getting rid of any. Anyone have any experience building one?

[Edited on 19-2-2008 by MagicJigPipe]




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Sauron
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[*] posted on 19-2-2008 at 02:03


I bought a locally build one for $1250 a few years ago. It has a decent pumping speed, and is thermostatically controlled with a digital display. It has enough capacity to cool the condenser of a 20 L Buchi or three benchtop (3-liter max each) Buchis. As these things are large and heavy I did not see any point in trying to import a used one from the US in the wrong voltage, the freight and duty would have eliminated any economies achieved. Better to have a 220V 50Hz one new. The price was IMO not excessive. Some of the name brand models in US are $10,000. But those are combination chillers and heaters and usually get down to -20 C or so.

The interesting ones are the cryo recirculators that replace dry ice/acetone or even liq nitrogen in some applications. Continuous operation of either an inline chiller or a cold finger/coil probe at -50 to -80 C. At the bottom end their ability to remove heat goes all to hell.

In principle these are "simple" machines. However I am fed up with DIY, life is too short and it is a lot easier to throw money at a problem than to play wrench-monkey.




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[*] posted on 19-2-2008 at 02:33


Quote:
Originally posted by Sauron
However I am fed up with DIY, life is too short and it is a lot easier to throw money at a problem than to play wrench-monkey.


Amen.

Fridge compressors are woefully underpowered. They just can't move enough BTU's to keep up.

And while chillers are ridiculous in price, they are an absolute necessity when working with ether or DCM unless its damn near freezing outside... those two solvents are simply too expensive to be allowed to evaporate.

I'm wondering if a 1/2 HP reef chiller could keep up with a ketyl still with the coolant running @ 0ºC.




Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.
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chemrox
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[*] posted on 19-2-2008 at 21:41


Quote:
- and then sold it on eBay for around $200. :mad:


I think I bought it. An older Buchi?




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[*] posted on 20-2-2008 at 04:22


I'm just afraid that if i try to do it myself i wpnt get a good vacuum seal and then what's the point? i might as well pour my chems down the drain (not that i'd do that)
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Sauron
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[*] posted on 20-2-2008 at 06:07


I have a couple of Buchi motor heads sitting in SF CA that I will likely never use. They are RE-120 I think. No stand, no bath, no glass. What I have by way of stands are all here in Bangkok and not worth the trouble to ship back. The correct stands for these are same as for the R-110.

The RE-120 takes the vacuum tube intended for a distributor head and vertical condenser, wither coil type or Dewar type, and can be set up for reflux, or for the E-type glassware which is rarely encountered. This is an intervening vertical trap surmounted by a U-tube and a descending coil condenser. This is for use with solvents prone to frothing and bumpings. For example, toluene is a notorious troublemaker in this regard.

The boiling flasks used are flanged rather than taper-jointed. Taper jointed flasks can be used with a special flanged adapter.

Of course these motor heads can be mounted on a Model R V-stand with or without jack handle, and used with a non-Buchi water bath of appropriate size. The expensive part is getting a glassware set together. These motor heads are 110V 60 Hz. They take a regular AC cord.




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[*] posted on 20-2-2008 at 07:23


Quote:
Originally posted by chemrox
Quote:
- and then sold it on eBay for around $200. :mad:


I think I bought it. An older Buchi?


Heh. It was a Buchi. I don't remember exactly when it was -- my records are on another machine -- probably a couple of years ago. If it went to someone here, and it's working out for you, then I feel better. :)
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Sauron
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[*] posted on 20-2-2008 at 09:12


For those unfamiliar with the evolution of the Buchi rotavap, the early and very common model still is Model R. I used one of these in the 60s. Its ancestry goes back to the late 40s or sometime in the 50s.

It was supplanted by the R-110 and variants.

Next came the R-111 whichhad a spring loaded stand.

After that came the R-140 series which was rather different, and interconvertible for the first time between R and RE type.

And that brings us up to the current Buchi line.

I have Buchi catalogs and parts lists and exploded drawings for most of the models from R110 to R-140 series.




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chemrox
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[*] posted on 20-2-2008 at 10:20


It's working fine-the seals are kind of old but replaceable. It's like an old man- a little slow to start but sweet and smooth once its cranking.

Sauron- got a pdf of the 110?

I would also like to get a dewar/cold-trap replacement for the condenser as an alternate cooling method.

[Edited on 20-2-2008 by chemrox]




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[*] posted on 20-2-2008 at 12:22


I know this is slightly off topic but...

Quote:
those two solvents are simply too expensive to be allowed to evaporate.


I don't consider ethyl ether expensive by any stretch of the imagination.

I would love to buy a new chiller but I just can't bring myself to spend that kind of money for something that isn't ABSOLUTELY necessary for many jobs in the lab and that is such a simple device. Maybe I shall do it myself for now (or buy a used one from an optical lab) and then when I have the appropriate funds I can buy a nice one.

In theory, I could create one that would at least be sufficient for most small to medium sized rotavap applications.

Then again, if I plan on spending the money to get a good rotavap then I suppose a chiller would just be a drop in the bucket in comparison.

What about normal distillation procedures? Should be worth it for that.




"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Sauron
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[*] posted on 20-2-2008 at 20:38


Chemrox, the top joint of the distributor head is 45/40, which is just a shorter European 45/50. 45/50 male joints fit it just fine. So, if you have a good sized Dewar with a 24/40 or (better) 29/42 joint, a simple adapter will couple it to the Buchi distributor head, this sort of glassware I have blown locally for cheap. (My glassblower has annealing oven etc. and a good source of ground joints up to 45/50.)

Buchi distributor heads often turn up on LabX and eBay as unidentified glassware. If you know what to look for you can pick one up cheap that way.

I will have to find the (physical) binder containing all my Bucho documents, I can then scan them and send to you or post them here.




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chemrox
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[*] posted on 21-2-2008 at 00:24


you are a prince! thanks again good friend!



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[*] posted on 21-2-2008 at 19:43


Quote:
Originally posted by chemroxI think I bought it. An older Buchi?


I just came across the correspondence for this auction. It was actually a Buchler, and I sold it in March 2004 -- for $120. :mad:
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chemrox
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[*] posted on 22-2-2008 at 10:23


No mine is Buchi 110. After seeing them for over $1000 for months I found it for around $200.



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[*] posted on 23-2-2008 at 09:31


The bath alone, I have paid more for than that.

The Buchi benchtop unit I still use is also a R-110. I gave my RE-131 with E-type glass to my ex-partner in New Orleans who lost it in Katrina, "sigh".

I could recreate it with one of those RE heads on the R-110 stand but the price of another new set of E-type glassware deters me. It's horrific.




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[*] posted on 23-2-2008 at 19:21


.....Speaking of recirculating chillers. Lately, I've been thinking of making one possibly out of a refridgerator condenser and some copper tubing

......Anyone have any experience building one?........

Building one from scratch is not so hard if you know refrigeration work but by the time you buy the components separately you will end up paying much more than buying a cheap water source package air conditioner (Florida Heat Pump) and reversing the condenser and evaporator.

A domestic fridge or freezer compressor ain't gonna cut it as you need at least a third to half a ton capacity.

An AC rated compressor will also not run efficiently at a low suction pressure/temperature so maybe 20 deg F is as low
as you could go paying close attention to the capacity curve
at any temp below 40 deg F which is were the rating is taken.
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[*] posted on 24-2-2008 at 00:54


I was thinking of using a small car radiator. I saw on the other day at the radiator shop that ws about 10" square. That, a fountain pump and a fan should do some decent cooling.



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[*] posted on 24-2-2008 at 01:47


A small automotive heater core can remove ~100W of heat with 2 decent 120mm fans in push/pull config. The guys who water cool their PC's on the cheap use this method quite often.

[Edited on 2/24/2008 by FrankRizzo]
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[*] posted on 25-2-2008 at 00:37


On rotavaps, you could take a glance at this site:

http://microblog.routed.net/2007/03/19/how-to-make-a-rotary-...

No idea how well the design as given would work, but as a starting point for a DIY machine, I think it's worth a look. A few relatively simple modifications should result in a fairly usable device, I think.
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[*] posted on 25-2-2008 at 19:45


"A small automotive heater core can remove ~100W of heat with 2 decent 120mm fans in push/pull config. The guys who water cool their PC's on the cheap use this method quite often."

It's probably a lot less when the water is way below boiling and ambient air temperature is so close to the water temperature.

That figure is probably at around 100C with 15C air blowing through.

EDIT
I'm sorry, I was thinking of a radiator. Do these work on basically the same principle?

[Edited on 25-2-2008 by MagicJigPipe]




"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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[*] posted on 26-2-2008 at 03:06


I got a cheapish (~£70) used rotary evaporator a couple a years ago. Unfortunately, I didnt get the pear shaped flasks since I was low on cash and thought I could wing it using standard rbf's. I drove 35 miles to the guy to collect it so I wouldn't have needed to pay any extra on postage.



Now, ^^^that is what I got at auction recently. I was th only bidder and is cost be £10.50 total. He SPENT £6.50 just on the postage and thats not even including packaging.

Basically, you know when you dont have a rotary evaporator, you have to set-up for vacuum distillation instead? Well, that's what the glassblower has done here: he's had to improvise. It says Quickfit but it's pretty obvious that it's been made out of a standard rotary evaporator column which has been modified. I didn't realize what this was until it arrived, but it's a funky piece of kit to have in my collection. It's all been done very professionally and doesn't look at all shitty or DIY like it's been done by an amateur/apprentice.

It's fucking weird though! Only the collection flask accepts 24/29 joint size;

the distilling flask has to be the same type as is normally used as the receiving flask on standard rotary evaporators.

Yes that's right, it's quite odd but still handy. I'm not going to write it off as just another piece of junk.




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[*] posted on 26-2-2008 at 16:50


I have two r-111 motors on their spring loaded stands, one is the larger type stand that houses a circular water bath and the other is the traditional triangle style base, they may be mix-matched as i received a couple of boxes of buchi odds and ends.

I want to turn one into a spit roaster, i thought it would be good as the torque is quite high but he rpm is low, also the level of the spit is easily adjustable because of the spring loaded arm. Both arms (as well asa third i have) however seem to have sticky handles (you know how you twist the handle to engage or disengage the height adjustment) and i was worried that this may be the reason they were all replaced. Does anyone know if this element of the system is easily repairable? (ie Sauron do you know if this element of the system is easily repairable, lol)




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