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Capillary rise in vaccume

by abhijitlohiya
Tags: capillary, rise, vaccume
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Jul18-07, 03:38 AM
P: 14
if gravitation is present, will there be a capillary rise of liquid in vaccume?
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Jul18-07, 05:44 AM
P: 175
Your question isn't clear.

If the capillary fluid 'wets' the capillary walls, there will be
a slight rise of the fluid due to the surface tension pulling the
fluid to adhere to more of the wall surface. When the
surface tension attraction force is balanced by the
force of weight of the lifted column the level will remain
at that point.

If you're talking about a manometer type of device, the
fluid will behave accordingly to the pressure difference
between the ambient pressure inlet port and the fluid
reservoir pressure i.e. the pressure on the other end of
the fluid column.

What would cause the fluid to rise if it were not vacuum?

What would cause the fluid to rise in the vacuum?

What would be the effect on the fluid if the device were
transported from a sea-level atmposphere environment
up to higher and higher altitudes until it was in a vacuum?

If the device works to measure something in a fashion
then that measurement process should apply continuously
over some range of measurements, with
vacuum (zero ambient pressure) being one ultimate case.

Of course some fluids have high vapor pressure in vacuum
at normal temperatures, so it's possible that the fluid
is not compatible with vacuum at the temperature you'd
be operating it... In fact the fluid would have to have
a significant surface tension otherwise it'd certainly
quickly 'boil' / 'evaporate' at comfortable temperatures in
Jul18-07, 06:23 PM
P: 880
didn't Einstein write a paper on this?

Jul19-07, 12:07 AM
P: 175
Capillary rise in vaccume

Quote Quote by rewebster View Post
didn't Einstein write a paper on this?
If so, I'm unaware of it, and wonder what his interest
would have been in the topic. It seems like something
that would be very straightforwardly explained by classical
hydraulics / gas law theories long before Einstein's time.

I know that fluid filled manometers were often used for
measuring pressures from atmospheric all the way down
to moderately high vacuum levels in lab settings,
and it wouldn't be uncommon to leave one connected
to one's vacuum system even once the pressure had
gone down to the point where the manometer wouldn't
be able to usefully measure it (p < 1 Torr).

Of course you'd need to use good vacuum pump oil or
mercury or something vacuum compatible in the tubes.
Jul19-07, 03:24 AM
P: 14
I mean if we keep a water container in vaccume and glass capillary tube is dipped in it will there be a rise of water in the capillary tube? If 'yes' is that height of rise same ,if the same expt is done outside the vaccume at the same place?
I am asking this because we explain the rise in capillary by considering the pressure difference at same distance above and below the liquid level in the capillary tube.

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