jmneissa - 8-5-2009 at 17:40
Okay so I have a small chemistry lab and I am looking into heating obviously open flame is out of the question. However there seems to be no clear cut
better method a heating mantle or a hot plate with oil or sand bath. While a heating mantle eliminates the need for the oil bath which also reduces
the risks of water or spilling hot oil. But a hot plate then allows me to magnetic stir a liquid being heated. I have read around on this site and
others what I have heard many people say is that for long distillations and refluxes that a heating mantle is better just because you eliminate the
associated risks with hot oil over long periods of time. For me though with a hotplate I can also heat Erlenmeyer flasks and beakers with liquids
which is nice but hot plate are notoriously inefficient because of minimum surface contact. I was wondering if any of you guys had a few towards
either one as I have seen both around the web site. Thanks
BromicAcid - 8-5-2009 at 19:58
No rule saying you cannot use both at the same time. Providing your mantle is the soft variatey and thin enough you can use your mantle atop your hot
plate and the stirrer will work fine. Additionally you can buy magnetic stir bars with rare earth magnets in them that will work even better through
the added material of the heating mantle. Finally they sell hard bodied heating mantles with air stirrers or eletric magnetic stirrers built in.
Also, consider an overhead stirrer, they work well and do not bog down like heating mantles and you can get decent vacuums while using one of them as
well. There are a number of options depending on your scale, but if you're going less than 5L there are the above options open to you and more.
jmneissa - 13-5-2009 at 16:47
Okay soory for the late reply I have been busy with exams... Okay well which one would you recommend is the better buy to start out with? I am sure
there must be one type that is better than the other...
Klute - 14-5-2009 at 01:00
I think a stirrer is going to be more practical in a first period, you can perform reactions ata variety of temperatures with good stirring, perform
vacuum distillations, etc. A mantle is good only for distillation IMHO, and you need stirring anyway, so better get the hotplate first, then when you
have enough money and you want to distill high boiling compounds, invest in a mantle you can combine with the hotplate/stirrer.
Arrhenius - 14-5-2009 at 19:40
I second the notion for the hotplate with a magnetic stirrer. I use oil baths (silicone oil, mineral oil or even vegetable oil), and find them to be
much more predictable than sand baths. If you can find one cheap, a crystallizing dish makes the best oil bath, but a beaker works too. A tip for
oil baths: throw a paper clip in there, and your magnetic stirrer will spin it and stir up your oil bath a bit.
Heating mantles are nice, but they only fit one size round bottom! I find them advantageous when using 1L flasks or large, which is quite seldom.
I've never had to use an overhead stirrer.
Mind if I ask what sorts of chemistry you're interested in?
[Edited on 15-5-2009 by Arrhenius]