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adorno
#1 Posted : 11/22/2011 12:38:25 AM

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Does anyone know what kind of vacuum or negative pressure standard lab glass can safely hold? Perhaps the question is much more complicated than this, as I tried Google and could not find a simple answer.

If SWIM was interested in learning more about rotary evaporation and/or vacuum distillation before taking any steps towards actually trying it, what types of things should SWIM begin from going forward so as to eventually proceed safely and without risk of implosions, etc.? (Besides having crackless glass!)
 

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benzyme
#2 Posted : 11/22/2011 1:50:53 AM

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rotavaps can handle deep vac, like 0.01 to 10 torr
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cjames
#3 Posted : 11/22/2011 2:34:01 AM

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Not used vacuums but i'd suggest only using apparatus (flasks, pumps etc) designed for the task in hand. No MacGyver setups just to be on the safe side Smile
At least you know it should cope under pressure/vacuum.
 
adorno
#4 Posted : 11/22/2011 11:34:55 AM

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Cjames, no Macgyver!, got it! Wink

Benzyme, thanks allot, rotary evaporators can hold a pretty intense vacuum you say. Let me ask you this then, there are dozens and dozens of "lab vacuums" for sale online, but I don't know enough to tell the ones designed for medical/dental/professional/plumping/automotive from the ones designed to be safely attached to rotary evaporator and/or vacuum distillation system. A few questions then, if you'd be so kind:

1. What is needed is (a) a vacuum, (b) a cold trap to prevent solvent from making it to the vacuum, and (c) a manometer to place in between your vacuum and rotary evaporation/vacuum distillation system so as to know your pressure (for nomographic bp calculations, etc.). Does this sound about right?

2. Would you please be kind enough to maybe send me some links (from ebay, from Google shopping, from Amazon, etc.) of example cheap ($100-$600) lab vacuums that could be safely attached to a rotary evaporator. Again, I only ask because as I said, I can see dozens and dozens of vacuums available online, but none of them specify that they are for safe attachment to rotary evaporators / vacuum distillation systems. Maybe this is simply a question of vacuum pressure range, in which case what would be safe ranges (in Hg, in Torr, etc.)

3. As for tubing, is all this pretty standardized with respect to lab glass? Is there a certain kind/size tubing one needs (along with tube clamps) for attaching a vacuum to a rotary evaporator?

I want to thank you again, and I'd love to hear from anyone else who has experiences using vacuums. Apparently these questions are too trivial for anyone to put simple answers to them up online, so this is really the only way I could think of to try and get answers to them. Perhaps this "new topic" I've created could be a catch all for safe vacuum use. I'm actually surprised, despite their steep cost, that more folks don't use rotary evaporators, apparently it saves quite a bit of time when stripping solvents and that, of course, is their irresistible appeal!
 
 
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