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I The meniscus in a square tube

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  1. Mar 11, 2016 #1
    Hi,
    I was wondering about the meniscus we get in a round tube, like a test tube or a boiling tube, or even a classic measuring cylinder. If we have a square transparent rectangle with water in - would this at all reduce the effect of the meniscus?
    How else is the effect of the meniscus reduced? I have been researching it and it suggested by putting it in a water bath.
    Does the material affect it? I know mercury inverts the meniscus, but is there any known substance which gives a flat reading?
    Thank you so much, even if you could just answer any one of these it's really appreciated :)
     
  2. jcsd
  3. Mar 11, 2016 #2

    berkeman

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    With a little Google searching, I found that the choice of the tube's material can give you a flat water meniscus. Search down this page for "meniscus"

    http://www.visionlearning.com/en/library/Chemistry/1/Properties-of-Liquids/222
     
  4. Mar 11, 2016 #3

    Andy Resnick

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    That's an interesting question. The physical quantity that matters is the curvature of the fluid-fluid interface because that's the energy of the surface, which is minimized. In the vicinity of the corners, if the corners are sufficiently square (say, the inside corners of a proper cuvette), the curvature can be sufficiently high as to interfere with wetting (movement of the solid-fluid-fluid contact line), leading to changes in the contact angle in the vicinity of the inside corner. As I recall, if the liquid wets the glass, the liquid is 'wicked' up the interior corners, so I suspect the opposite occurs when the fluid does not wet the glass.

    http://pubs.rsc.org/services/images...e/2015/CC/c5cc01480h/c5cc01480h-f1_hi-res.gif

    It's easy to check- I'll try and remember to try this when I get back in the lab (in a week).

    About your other question- the contact angle can be (somewhat) controlled- that is, it's easy to make a surface wetting or nonwetting for (say) water, but it's not so simple to make a surface that water forms a contact angle at a specified angle.

    http://pubs.rsc.org/services/images...cleimage/2011/LC/c1lc20388f/c1lc20388f-f6.gif

    Pickering emulsions have solid particles pinned at a fluid-fluid interface, in some cases the contact angle is 90 degrees, but I don't know the secret recipe.
     
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