Re: vacuum pump

> > A note: My improvised aspirator could certainly cause water to boil
> > (isn't this around 0.5 cm Hg?). This was long ago, and I was trying
> > to make low-pressure gas lamps to light them with electrostatic
> > machines (the idea worked). I had a valve in the vacuum line, and
> > always closed it before closing the water, of course, otherwise
> > the result would be a lamp filled with water...

>         Very interesting, and would sure like to see "plans" for the
> hopefully suitable for making a copy.  Question, though:  Seems to me
> that in order to make water boil you would have to reduce the pressure
> below the vapor pressure of water in the residual gas at the temperature
> of the water.  How can a device operating on water do this?
> Ed

I'm not saying it can work, but, if the water were moving fast enough, it
could capture the molecules by collision (like a diffusion pump or a turbo

I'd expect an aspirator to get to the vapor pressure of the working fluid,
and that's it, from a practical standpoint. As for boiling water at room
temp with an aspirator? This I'd like to see. If the water were warm (say
40 C), and the aspirator were cold, (say 10-15 C), it could work, and these
are reasonable temperatures, particularly in the summer. Where in Brazil
are you Antonio? one of those places where the temperature never varies
from 35C, like Manaus.

Vapor pressure of water at 20 C is 17.5 torr, at 37 C (body temp) it is 47
torr (about 19-20 km altitude)

By the way, boiling water in a vacuum brings up the interesting observation
that if you depressurize in space, your blood won't boil (The static
pressure in you veins is high enough to keep the pressure above the vapor
presssure at 37 deg). Your saliva will boil off, as reported by the few
people who have depressurized and lived to tell about it.