kemikallyimbalanced
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Mag stirring with a mantle
I have to do a reaction soon that will require mag stirring with a mantle. How would that be possible? I have a few soft mantles and a stirring plate
that also heats. Could I just place the mantle on the plate or would that damage it? I was thinking about heating up the plate also but it still may
get burned huh? What if I keep the mantle a few ml above the plate?
[Edited on 16-4-2007 by kemikallyimbalanced]
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evil_lurker
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Every mag hotplate I've seen is thermostatically controlled.
If it'll stir thru the mantle, simply kill the heat on the plate and you'll be fine.
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Sauron
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You can stir through a mantle.
Just keep the heater part of the stirrer hot plate switched off.
Or get an overhead stirrer, much better.
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Klute
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If your stirrer is strong enough, it will work, that's what i do. But you can't set the stirring to strong or the egg bar will loss it's "catch" and
just bounce everywhere in the flask... When strong stirring is needed, i try to use a oil bath as long as it possible...
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kemikallyimbalanced
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Thanks everyone!
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chemrox
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| Quote: | Originally posted by Sauron
Or get an overhead stirrer, much better. |
I've had quite a time tweaking mine so it keeps going at the proper speed without monitoring. I think part of the problem is with the way my rack is
.. it's not a permanent installation yet. It's made from a couple of stands with horizontal rods. I think this arrangement allows a little flex in
the uprights that shouldn't be there. There's an inherent issue that arises between the bearing and the motor. A certain amount of torque is
required to overcome the bearing friction. The bearing friction is a function of the materials, the rod thickness v. the bearing i.d. and the
alignment of the motor shaft with the rod. The rod I have has slight variations in diameter along its length so the frictions is different at
different heights. If the bearing, rod and motor shaft aren't in close to ideal alignment, too much of the torque goes to overcoming friction of
mis-alignment. Slight changes in this result in one kind of response or another. Either the sudden reduction in friction is translated to rpms or a
sudden increase causes the motor to stop. Also, poor alignment causes excess power draw making heat.
I'm planiong to build permanent racks using small diameter pipe, T's and flanges. If necessary a few "deadmen" could be run to the wall near the top
to prevent flex. I'm hoping this will allow the overhead stirrer to be more useful. Meanwhile, any long stirs will have to be done with stirring
bars. I got a flat bottomed flask for the purpose.
I reiterate what everyone said about the use of stirring bars. I have a stir bar spinner and a combination hot plate stirrer. Both stir through
mantles with little attenuation. If you get a flat bottom flask the option of using the hot plate is also there and you can use the heat directly or
with a fluid or sand.
[Edited on 19-4-2007 by chemrox]
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