Ophidean
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Overhead stirrer
I am not familiar with overhead stirring and i would like to know how to accomplish this. I used to work with magnetic stirring and reflux condenser,
but now I am setting up a 12L 3-neck round bottom flask in which my magnetic stirrer wont suffice anymore(not enough power).
Now how do i use overhead stirring in this? Seeing as how I understand it you put some kind of stir-bar from the top through the neck, but at this
place there will be a liebig condenser?
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redox
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Is it not possible to put the stirrer in the center neck, and put the condenser on a side neck?
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Ophidean
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Hmm I guess ill just have to rearange then.
But this will not make it less efficient?
Might be a crazy thought, but just feels that way when you use a neck that is diagonal and not straight.
And a second thing: How would i use an overhead stirrer, because normally you can just put a stopper on a neck, and use a magnetic stirrer, but with
an overhead stirrer you will have to keep the neck open for the stirbar? (It of course needs to be sealed for reflux condensing)
[Edited on 8-6-2011 by Ophidean]
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azo
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Of course you can use mechanical stirring in the centre neck
if your setting up for simple distilation you could use a claisen still head.
regards azo
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darel
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They are called stir bearings and are ground glass and air tight. I have one for a 19mm driver into a 45/50 ground glass joint. They are lubricated
with silicone oil or you can buy them in teflon. This solves the air tight problem. for stirring with overhead. Now you can have a condenser on one or
both the remaining necks. The gasses will only go to where they can escape to atmospheric pressure the easiest. Here are a few for sale on ebay
currently
http://shop.ebay.com/i.html?_from=R40&_trksid=p5197.m570...
I have a fancy spinning band distillation column that has the spin shaft run through the reflux condenser on top. But this is a custon piece and very
costly.
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Ophidean
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Quote: Originally posted by darel  | They are called stir bearings and are ground glass and air tight. I have one for a 19mm driver into a 45/50 ground glass joint. They are lubricated
with silicone oil or you can buy them in teflon. This solves the air tight problem. for stirring with overhead. Now you can have a condenser on one or
both the remaining necks. The gasses will only go to where they can escape to atmospheric pressure the easiest. Here are a few for sale on ebay
currently
http://shop.ebay.com/i.html?_from=R40&_trksid=p5197.m570...
I have a fancy spinning band distillation column that has the spin shaft run through the reflux condenser on top. But this is a custon piece and very
costly.
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Ah yes I see, and what would be the use of running water through them (because they seem to have connectors for this)? Or do they just have other uses
except stir bearing too.
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Lambda-Eyde
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| Quote: Originally posted by Ophidean |
Ah yes I see, and what would be the use of running water through them (because they seem to have connectors for this)? Or do they just have other uses
except stir bearing too. |
It's for cooling. The bearings can get really hot from the friction, so water cooling is mandatory. Some models use a small reservoir you can fill
with glycerol or paraffin, which serve as a coolant instead of using water.
Just run some tubing from the condenser to the bearing.
| Quote: Originally posted by darel | I have a fancy spinning band distillation column that has the spin shaft run through the reflux condenser on top. But this is a custon piece and very
costly.
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Pictures, please!
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Ophidean
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Ok thanks! And last question, what kind of overhead stirring would I have to purchase for this, ive seen some on ebay, but they seem so small, are
they powerfull enough for a 12L flask?
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Lambda-Eyde
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Buy one with a blade that fits in the flask (and through the joint), and most importantly, with a bar that will fit through your bearing.
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Ophidean
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| Quote: Originally posted by Lambda-Eyde | | Buy one with a blade that fits in the flask (and through the joint), and most importantly, with a bar that will fit through your bearing.
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Of course, but I meant like, if you have a 12L flask, filled for like 6-8L. What kind of overhead stirrer would you take? (I meant in power of
course. 40W, 60W, 100W?)
[Edited on 9-6-2011 by Ophidean]
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darel
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Spinning Band Distillation Column
I believe this is what I got
http://www.brinstrument.com/fractional-distillation/fraction...
It would be the first one
I am still lookng for the interface and software to use the thing. Ebay has a few different types and can't figure out which one is correct. Also need
an adapter to go from a $50/30 spherical to 24/40, 29/42 or 45/50. Ebay has given no such luck and I'm still waiting on a response from the company
for hard/software. Here is a link to the thing disassembled and some of the parts.
http://s287.photobucket.com/albums/ll149/darelgreen/Spinning...
[Edited on 6-9-2011 by darel]
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albqbrian
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Or...
Just get a cheap electric drill and use the attachment for stirring paint.
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Dr.Bob
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If you are looking for the actual teflon paddles and stirring rods and bearing shafts, I have a few sets of them for glass flasks, in 24/40 and
several larger sizes. The 24/40 is not much use, as the paddles that fit through that are not big enough to do much stirring, so most people use
larger ones.
A great place to see what is available for labware is the Chemglass.com website, they have their entire catalog on the web, with photos and
descriptions, so you can find a part number or name for what you want along with similar items that might also work. For example, the one below is
for a nice overhead stirrer system. I don't have any stirrer motors left, but have the glass shafts, bearings and paddles left.
Bob
http://www.chemglass.com/product_view.asp?pnr=CG-2039-A-10
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