AndrewOfWallachia
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Heating a round bottom flask
So my distillation glassware finally arrived today, I was really excited, I set it up for a simple distillation (my first ever one so I tried just
distilling water), however because I only have round bottom flasks for distilling I used a waterbath under the 180w hotplate of my newly acquired
magnetic stirrer which according to the instructions can reach 300C, however I couldn't get the water in the flask to boil because the waterbath was
also boiling at 100C and it would evaporate instead really transferring enough heat to the water in the flask, yes, in retrospect, this was REALLY
obvious, and I should have thought of that before, but as a complete newbie to distillation I wanted to ask the following:
1. Could I place the Round Bottom Flask directly onto the hot plate? (I have severe doubts about this since there will only be a really small contact
point between the flask and the hot plate, also I am afraid I might run the risk of cracking the glass)
2.Would it work if wrapped the bottom of the flask in thermally conductive material (Tin Foil) and then placed it directly onto the plate? (I have
about the same doubts about this working, minus the glass cracking since the heating will be much more spread out)
3.If there's is no other method, I'll use an oilbath. Any tips, tricks, or important things I should know before using oil baths?
Thanks in advance, brothers!
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Texium
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An oil bath is the most effective method. Mineral oil is cheap and readily available. It heats up fairly fast, and it’s an effective medium for
transferring heat to a flask up to about 200 °C. The only downside is it’s messy.
A less messy (but not nearly as effective) method is to use an “air bath,” which basically means you clamp the flask a couple cm above the surface
of the hot plate and wrap a skirt of aluminum foil around it so that the air between the hot plate and the flask is trapped. Putting the flask
(whether wrapped in foil or not) directly on the surface of the hot plate risks stressing the glass and will inevitably lead to bumping at best.
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Texium
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Thread Moved
6-12-2023 at 13:32 |
DraconicAcid
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A sand bath isn't as effective as an oil bath, but better than an air bath, and less messy than an oil bath.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Rainwater
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Using a water bath to boil water is a common practice as over heating isnt a problem.
But you need to add something to the water bath
Saturated table salt will up the temp to about 108c
50/50 antifree will get you to 125c
Baby oil will get you to 250-275c
Each has their pros and cons.
If you use baby oil just remember that 100ml at 25c is about 300ml at 200c.
And in a sealed appratus is great for getting a little extra vacuum.
"You can't do that" - challenge accepted
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Sulaiman
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130ml?
CAUTION : Hobby Chemist, not Professional or even Amateur
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