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?redox - 8-6-2011 at 14:28
Is it not possible to put the stirrer in the center neck, and put the condenser on a side neck? Ophidean - 8-6-2011 at 14:52
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]azo - 8-6-2011 at 20:34
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 azodarel - 8-6-2011 at 21:21
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
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. Ophidean - 9-6-2011 at 01:28
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
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.
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.Lambda-Eyde - 9-6-2011 at 03:01
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.
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.
Pictures, please! Ophidean - 9-6-2011 at 03:41
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?Lambda-Eyde - 9-6-2011 at 03:48
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.Ophidean - 9-6-2011 at 05:25
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.
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?)
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.
Just get a cheap electric drill and use the attachment for stirring paint.Dr.Bob - 15-6-2011 at 09:11
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.
