mycotheologist
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Using a propane torch to heat glassware
I haven't got a bunsen burner and can't afford a heat gun at the moment. I have a propane torch but it seems a bit excessive. I suppose I could
position the flame far enough away from the flask so as not to damage it and heat the contents too rapidly. Have any of you done this? Are there any
tricks for insulating the flask against excessive heat? I'm making glacial acetic acid from sodium bisulfate and sodium acetate so I only need around
300C to melt the bisulfate.
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GreenD
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It should work fine, are you going to be holding the torch the entire time?
The glass isn't going to break before it gets red / distorts, I wouldn't think - unless you have low quality glass.
If you are going to be holding the torch or at least closely watching it the entire time, just keep the heat close enough to melt the bisulfite, but
no closer.. The best way to do this would be to make sweeping motions across the bottom of the flask, or have the flask turninig while you heat it to
evenly distribute the heat. The latter will be tricky if you don't have something to do this for you, or some really nice oven-mits.
ʃ Ψ*Ψ
Keepin' it real.
Check out my new collaborated site: MNMLimpact.com
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Endimion17
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Gas torches must never be used for heating laboratory glassware such as flasks. That's what flameworkers do when modifying the glass, but they do it
carefully, by preheating it in a diffused flame.
Touching the reasonably cold glassware with a jet of premixed air-fuel blue flame is a disaster waiting to happen.
If you can't modify the flame with an air intake vent to avoid this flame:
or don't have a heating mat (asbestos, ceramic fibres), wrap the flask with two layers of dense steel net which will dissipate the direct heat, and
don't immerse the netting into the blue jet.
GreenD, the glass will break way before it starts glowing. Actually, when it glows, it's already half way to a liquid and it can't
break.
I'm saying this for all of you - be careful with advices you're giving to someone. I see almost none of you respect the standard safety protocols and
just share youtube disinformations which can hurt someone badly or at least cost some money.
[Edited on 13-5-2012 by Endimion17]
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mycotheologist
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Thanks for the warning, I'll come up with a different method than heating the flask directly. I can probably just use the torch to rapidly heat a sand
bath or something. I don't wanna wrap the flask in steel because I need to be able to see the bisulfate melt. I'm just trying to figure out a decent
means of heating an intermediate heat source (like a sand bath) with the torch. Heating the sides of the metal pot will result in massive heat loss
and uneven heating.
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Endimion17
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You can see the melting allright. Check this out.
I used a relatively weak flame and I think one sheet of steel netting. As you can see, everything inside is visible.
It was a poor man's setup, but safe enough.
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Dr.Bob
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Yes, you need a flame diffuser and do not touch the flask with a flame, especially if a thick walled type like Chemglass flask. Thin walled flasks
actually do much better with flame, thick walled flasks are designed for heating mantles or oil baths. But I have had at least one person crack a
flask heating with a flame when full of water, much more dangerous with organics inside. I would never heat a organic liquid with a flame, acetic
acid might be OK, but I would do it outside, as if it does break inside, there could be a big fire.
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sargent1015
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Edminion, I really like the video, good way to demonstrate properties (with techno music  )
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