alyks
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Use of Flat-bottemed flask in Reflux.
I was wondering if it would be possible to use a Flat-bottomed Flask for a normal Reflux, Reflux with drying tube, and Reflux with a Separatory funnel
connected to a Claisen adaptor. I know you have to use Rb-flasks for anything with a vacuum, but what about this?
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roamingnome
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a good quality glass like "pyrex" for sure....
if it has seems like a jar... then brakey brakey... if you heat it unevenly
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joeflsts
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I have also used a flat bottom flask on occassion. It works.
Joe
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Sauron
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It's normal to use a flat bottomed boiling flask for reflux if you are heating with a hot plate rather than a mantle, See Corning Pyrex catalog for
many examples of such flasks with standard ground glass joints.
Your addition funnel should be the pressure equalizing type with glass stopper closure and a standard taper joint. PTFE stopcocks better than glass
usually (no grease required.) Choice of condenser depends on what you are refluxing. For very volatile or low boiling material you need a very
efficient reflux condenser. There are many types.
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alyks
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I have a jointed Separatory funnel with a glass stopcock. Could I buy a PTFE stopcock replacement on ebay? For example: http://www.agile-fx.com/catalog/stopcock.jpg Which is selling on ebay.
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vulture
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Don't bother. Just wrap your glass stopper with a bit of thin teflon plumbing tape, that'll stop it from getting stuck.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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kaviaari
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I think that sometimes the flat-bottomed flasks are way more useful. You don't have to fool around with oil or water baths. Only take the bottle and
put it on the heating plate. Most of the time I'm using erlenmeyers with grounds joints as reaction flasks. And when using erlenmeyers you don't have
to have cork rings of any kind. Although cork rings can be replaced quite easily with tape rolls, beakers etc.
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alyks
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| Quote: | Originally posted by kaviaari
I think that sometimes the flat-bottomed flasks are way more useful. You don't have to fool around with oil or water baths. Only take the bottle and
put it on the heating plate. Most of the time I'm using erlenmeyers with grounds joints as reaction flasks. And when using erlenmeyers you don't have
to have cork rings of any kind. Although cork rings can be replaced quite easily with tape rolls, beakers etc. |
You can put the Flat-bottomed flask directly on hot plate? I had no idea.
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chemrox
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| Quote: | Originally posted by vulture
Don't bother. Just wrap your glass stopper with a bit of thin teflon plumbing tape, that'll stop it from getting stuck. |
Don't do this, it might work briefly but is the wrong approach. Use silicone stopcock grease. A tube will last years.
a pressure equalizing addition funnel can be improvised with a straight vacuum adapter and cork and tube or gas release joint (basically a st joint
closed with a fitting for tubing). Run a length of tubing between the vacuum adapter and the top of the sep funnel. Or buy one used .. I picked up
three of them for under $10 apiece.
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evil_lurker
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I have some 10 packs of teflon joint sleeves, size 24/40 for $20 with free shipping if anyone is interested.
They are vacuum tight and beat the hell outta stopcock grease... no hard to clean up residue!
[Edited on 5-2-2007 by evil_lurker]
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