The handpump claims it can go down to 25mm Hg. That seems unlikely to me. I 
suspect it's more likely it'll go down to atmospheric - 25mm HG. I could 
very well be wrong. Having never done vacuum work, I honestly don't have "a 
feel" for what the values mean. By that, I mean, I assume you get a feel for 
how strong a vacuum is sort of like comparing the current temperature to a 
number on a thermometer gives you a feel for temperature. I'm sure after 
doing some vacuum work and then opening it up and hearing how much air gets 
sucked back in and how strongly, will give me some idea of what the 
different values mean.

I suspect a round bottom flask is better suited for that kind of pressure, 
since rounded surfaces tend to take negative pressure better (which is why a 
lot of mini-subs use rounded windows). I'm actually more concerned with 
distillation tubes and such (as they're much more expensive than flasks).

How does one find out the negative pressure a piece of glassware can 
withstand? I mean, short of the obvious of keep going until it implodes...

Thanks


"Tom McCloud" <mccloud-tom@worldnet.att.net> wrote in message 
news:5ufjo21l36du0uqo97e0s7ng7a1saejotk@4ax.com...
> On Wed, 20 Dec 2006 10:44:21 -0600, "Fredo" <fredo@hotmail.com> wrote:
> 
> > What sort of vacuum pressure can typical lab glassware handle?
> 
> I routinely do rotary evaporation in 3 liter round bottom flasks at
> 3 torr.     Smaller glassware will handle lower vacuum.    A 1 liter
> RB without scratches can be used at 100 mM Hg.
>