JensenJ - 11-8-2016 at 17:04
I've realized in the last several years, I've never once used my small round bottom flasks. The flat-bottom versions are just so much more convenient.
They stand up on their own, no special sized heating mantle required for them. Sit easily on any universal hotplate with stirrer. It's been making me
think about getting rid of my smaller round bottoms because I never use them and they are just taking up space.
I see the advantage to using purely round bottom maybe in the industry, but for small lab work?
Metacelsus - 11-8-2016 at 17:10
Round bottom ones are more robust to vacuum and pressure.
diddi - 11-8-2016 at 17:23
I have moved towards FBFs because I don't have a good set of mantles. oil baths work well, but they are such a nuisance to set up and clean up after,
so I put money into a high quality stir/hotplate and work with it fairly effectively imho.
DraconicAcid - 11-8-2016 at 17:27
It's much easier to get the last drops of stuff out of a round-bottom than a flat one. Also, for certain gas-generating reactions, I have found that
they proceed smoothly in a round-bottom, whereas they act like volcanoes in Erlenmeyers.
Dr.Bob - 16-8-2016 at 09:45
As stated, round ones are stronger, handle vacuum safer, and are easier to transfer from. Magnetic stir bars also work better in the round ones, at
least oval ones. Flats may work better with the cheaper simple rod or hexagonal stir bars, though. But flat ones are fine for many purposes.
Whatever works, unless you are under vacuum, then round is much safer. I have a few 24/40 flat bottom ones left if anyone likes them, I don't use
them much.
XeonTheMGPony - 16-8-2016 at 10:43
lets not forget more exposed surface area Vs volume as well.
PHILOU Zrealone - 16-8-2016 at 11:12
Flat holds itself stable on a bench or on the gas stove without holder...
I have a 5L and 10L distillation pyrex flat bottom flask and it works like a charm for distillations, I only have to care for holding the glass
condenser in place...the glass vigreux column holds wel in place (vertically) once stuk into the very stable flask
Melgar - 16-8-2016 at 23:41
I mostly only use my small round ones as receiving flasks anyway, so they don't tend to need heating. I have a whole bunch of rubber flanges that I
can use to set RBFs on and not worry about them tipping over. Also, RBFs can have magnetic stirring going on when they're tilted, which isn't
something you need to do super often, but it's really convenient to be able to do it when you need to. That being said, I still have plenty of
flat-bottoms just because it's so much easier to set them up on a flat hotplate.
As far as the "structural integrity under vacuum" issue, unless the glassblower really fucked up, this is only really an issue for flasks above a
liter or so, and using smaller flasks is going to lower your risks FAR more than whether you have a flat or round bottom flask.
Also, if you have the right type of stirbar, RBFs are somewhat quieter, since flat-bottoms usually have a ripple effect going on on the bottom.