jharmon12
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Magnetic Stirrer and Ice Baths
I want to use a magnetic stirrer to stir an acid solution that must be contained within an ice bath. My normal process is to create a salt/water/ice
bath in a 1000 ML beaker. I then use a 500 ML beaker to contain the acid bath. The bath must be kept cold, so the 500 ML is submersed into the 1000
ML. I then use a glass rod and continually stir for the whole process. Pretty simple.
I want to buy a magnetic stirrer and use it going forward. I want to be able to stir the acid solution with a magnetic stirrer while keeping my acid
bath cool. How is this done normally so that the stirring rod will still work with ice water between it and the magnetic stirring machine?
Thanks,
Joel
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Magpie
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I do that kind of thing all the time with my Corning magnetic hotplate-stirrer. I heat an oil bath in a ss bowl on the hotplate and then have a glass
RBF w/reactants sitting in the oil bath. I have a stir bar in both vessels, and they both work fine.
The single most important condition for a successful synthesis is good mixing - Nicodem
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jharmon12
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Not sure I follow. So how much distance from the magnetic stirrer and the actual stir bar can you have on your corning?
Thanks,
Joel
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Magpie
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The stir bar in the RBF is probably ~1" from the hotplate surface. I don't know what the outer limit would be.
The single most important condition for a successful synthesis is good mixing - Nicodem
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jharmon12
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Thanks, that is mucho help. What model corning do you have? Sounds like what I want my wife to get me for Christmas.
Thanks,
Joel
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Magpie
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It's a PC-320. I just tested it with a 1" stir bar in an empty beaker and it lost coupling at about 1.5" above the hotplate surface.
I bought the hotplate about 10 years ago off eBay for $100-120 if IRC. It's given me very good service.
The single most important condition for a successful synthesis is good mixing - Nicodem
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jharmon12
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Thanks a lot Magpie. I now know what I want for Christmas and I know what my capabilities are with this unit.
Regards,
Joel
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zed
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Flat bottom beakers? Generally, you wouldn't worry about keeping your acid beaker's bottom, in direct contact with your ice-water. Usually, no
gap between beakers is required. Direct cooling of the large areas on the sides of the reaction beaker is adequate. After all, you are stirring.
Magnetic stirring is great, but it doesn't like gaps. Even with my Neodymium Supermagnet Stirbars, I lose strong magnetic coupling pretty quickly
with distance.
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bfesser
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How much longer before we get our high-Tc magnetic stirrers?
[edit] <a href="http://www.atmi.com/lifesciences/products/mixers/levmixer.html" target="_blank">This</a> <img
src="../scipics/_ext.png" /> isn't exactly what I had in mind.
[Edited on 14.12.13 by bfesser]
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DJF90
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I was wondering how effective it might be to switch out the stock magnets in a hotplate stirrer with SmCo ones. They'd handle the heat sufficiently
well...
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Mailinmypocket
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I also use this type of system often except I avoid using any metallic receptacle to hold the bath as it interferes with the magnetic fields.
The best method I have come up with so far is to buy the biggest (not longest, but the fattest) magnetic stir bar possible that fits in the bath and
place another stir bar in the reaction vessel and place that as close as possible to the baths stir bar.
The magnetism from the large bar helps the one further away to spin better without decoupling.
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