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Capillary rise in vaccume

  1. Jul 18, 2007 #1
    if gravitation is present, will there be a capillary rise of liquid in vaccume?
  2. jcsd
  3. Jul 18, 2007 #2


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    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
  4. Jul 18, 2007 #3
    didn't Einstein write a paper on this?
  5. Jul 19, 2007 #4


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    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.
  6. Jul 19, 2007 #5
    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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