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Author: Subject: Heating flasks with open flames...
evil_lurker
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[*] posted on 8-2-2006 at 08:13
Heating flasks with open flames...


I need to do a high temp distillation because I do not have a vacuum pump.

I was thinking of using an open flame from a camp stove on a 1L RB flask.

Should I get some window screen and use a support ring to spread the heat out?

I'd hate to fire it a bit too hard and end of having the thing crack and send flammable liquid everywhere.

[Edited on 8-2-2006 by evil_lurker]
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Magpie
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[*] posted on 8-2-2006 at 08:23


Normally a wire screen with some type of fireproof fabric built into a circular pattern in the middle of the screen is used when heating a glass flask with a flame. Check out the chemical supplier online catalogs. I think these help spread out the heat to the flask.

If you have trouble getting your temperature up at the stillhead take some fiberglass insulation (1" thick) wrap it in aluminum foil and then wrap this blanket around the flask and neck. What is the expected boiling point?

[Edited on 8-2-2006 by Magpie]




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evil_lurker
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[*] posted on 8-2-2006 at 08:30


170-180C

I need to get this done ASAP and basically I was just hoping for a quick fix that would get me by until I can get the proper equip.

I'll take the burner and set it off from the bottom of the flask a few inches and see what happens.

I might even try a sand bath.
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Magpie
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[*] posted on 8-2-2006 at 08:40


You may already know this but it is something I learned at school, forgot, and then had to relearn the hard way:

The placement of the thermometer bulb in the stillhead is critical for accurate temperature measurement. The top of the bulb is to be level with the bottom of the angled joint in the distillation adapter. Consult any good organic lab manual if you don't understand. It will have a diagram showing this.

BTW, I had to use an insulation blanket when distilling nitrobenzene, bp = 210C.




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evil_lurker
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[*] posted on 8-2-2006 at 08:57


Yeah I was aware that the thermometer must be placed a certain way, although I was not exactly for sure where.

Makes sense, just put the top of the bulb on the bottom of the exit hole.

I might have something that would work in a pinch... I'm off to go look at some exhaust repair kits... the fiber should be fairly heat resistant... in fact according to victor automotive products it should be good to go up to 1200C..

[Edited on 8-2-2006 by evil_lurker]
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