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Trying to understand colloids microscopically and macroscopically

  1. Jul 28, 2007 #1

    neu

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    I've been reading a little about this rather new subject (to me), and I'm quite confused.

    I understand that a colliod is broadly dfined as a substance consisting of a dispersive phase, ie very finely ground gold dust, in a continuous phase, ie water.

    I'm informed that colliods are especially important for macroscopic measurement of microscopic effects (whatever that means). Could anyone provide an insight, or a good source of information on this topic?

    I apologise for the lazy post, but as you can see my knowledge is rather limited. I'm a 3rd year physics student and I've never heard of this field of study.
     
  2. jcsd
  3. Jul 28, 2007 #2
    they're probably a good way to see Brownian motion
     
  4. Jul 28, 2007 #3

    bel

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    There, I suggest any undergraduate book on "general" chemistry, those books usually have a few pages devoted to colloids.
     
  5. Aug 1, 2007 #4
    a colloid is a suspension of nanoparticals in a liquid that doesn't settle out
     
  6. Aug 1, 2007 #5
    colloidal particles lie between 1 to 100 nanometer. they can be seen only under ultra microscope
     
  7. Aug 2, 2007 #6

    chemisttree

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    I believe the upper size limit is a micron (1000 nanometers).
     
  8. Aug 5, 2007 #7
    a colloidal solution or a colloid is transluscent and causes the tyndell effect, an effect seen when light is dispersed through the canopy of a forest.
    an example for a colloidal sol. is milk.
     
  9. Aug 6, 2007 #8
    "I'm informed that colliods are especially important for macroscopic measurement of microscopic effects (whatever that means). Could anyone provide an insight, or a good source of information on this topic?"

    It can prove quite difficult to measure microscopic properties of some colloidal systems, but macroscopic measurements such as rheology or light microscopy (crossed polarised light) can be used to infer molecular and sub molecular behaviour.
     
  10. Aug 6, 2007 #9
    say for example one person dies, the whole world mourns.:eek:

    If i am wrong please correct me
     
  11. Aug 8, 2007 #10

    chemisttree

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    The only experience I have in this field is the measurement of BTEX compounds (Benzene, Toluene, Ethylbenzene, Xylene) using colloidal cadmium sulfide particles. The unexposed particles fluoresce with a color characteristic of the band gap of the CdS particle. The fluorescence is attenuated, by quenching, when BTEX compounds are present in extremely low concentrations. Here the measurement of a microscopic binding event is measured macroscopically. These are often referred to as 'quantum dots'. Immunolabelling of these dots will cause a change in fluorescence when the antibody-modified quantum dot binds to an antigen.
     
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