Re: does a siphon work in vacuum?

[Ludwik Kowalski <kowalskil@MAIL.MONTCLAIR.EDU>]

I also think that by changing the pressure of air
around the vessel with a liquid, such as Hg, would
have a negligible effect on the rate of syphoning.
In a vacuum, the pressure at the mouth of the upper
ending of the tube (p1=rho*g*h) is still higher than
the pressure (p2=0) at the mouth of the lower
(hanging) ending. The difference due to the air
pressures at these two locations is usually
negligible. Thanks for a good question, Josip;
I might use it on an exam.
Ludwik Kowalski

On Sunday, Mar 14, 2004, at 13:35 America/New_York, John Denker wrote:

> Quoting Josip Slisko <jslisko@FISMAT1.FCFM.BUAP.MX>:
> ...
> > According to the (1), the maximum lenght of the short arm is the
> > barometric height of used liquid and a siphon would not work in
> > vacuum.
> >
> > According to the (2), for a very cohesive liquid, the maximum lenght
> > can
> > be bigger than the barometric height and a siphon would work in
> > vacuum.
>
> It *is* possible to have negative pressure in a liquid.  I get 600
> hits from
>   http://www.google.com/search?q=homogeneous-nucleation+liquid+bubble
>
> Such a state is only metastable against phase-separation.  But
> sometimes
> metastability is good enough.  A "D" battery is at best metastable
> against self-discharge, but people buy "D" batteries all the time.
>
> Siphoning in a vacuum is presumably somewhat tricky, but I would
> not be at all surprised to see it done.  I can't think of any law
> of physics that would prevent it.