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Sugar Mixture

  1. Jun 15, 2011 #1
    Does a mixture of sugars have a Eutectic?
     
  2. jcsd
  3. Jun 15, 2011 #2
    I don't know the answer to this one, but my first guess would be no they are miscible in all proportions, since there are many commercial mixtures of treacle and syrup out there.
    Toffee and fudge, of course, contain water and fat as well.
     
  4. Jun 15, 2011 #3
    A eutectic is a mimum where the temperature of solidification from the liquid phase is least for different proportions of two compounds. The example I'm familiar with is lead and tin. I imagine two missible liquids like water and ethanol will also have a eutectic, or two different sugars like lactose and dextrose as well, though I really don't know.
     
  5. Jun 15, 2011 #4
    I know what a eutectic is.

    You do not get eutectics when the two substances are miscible in all proportions.
     
  6. Jun 16, 2011 #5

    DrDu

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    Only if they are miscible in all proportions in the solid state. I don't know whether this is true for sugars. Furthermore, the determination of the melting point for sugars is quite a mess as they tend to exist in various configurations (alpha and beta aldoles, dimers ...) and for many sugars the melting cannot be separated from decomposition.
     
  7. Jun 16, 2011 #6
    I don't know what ya'all are talking about, Studiot. You can't even separate lead and tin into regions of solid state and liquid state but must include two others. There are regions on the ratio vs. temperature graph that are mixtures of both solid and liquid phase.

    Lead and Tin have a Eutectic, they are missible in all proportions at the temperature above that of solidification of the maxima of both Lead or Tin.

    ...I just wanted to know how the manufactures of Pop Rocks decided to mix 3 sugars together to make their product successful...
     
    Last edited: Jun 16, 2011
  8. Jun 16, 2011 #7
    Here are sketches of two phase diagrams to clarify matters. One is the tin-lead system the other is the copper-nickel system.

    As you rightly observe the tin-lead system has a eutectic point at 36% lead.
    This is because liquid tin and liquid lead are miscible in all proportions, but solid tin and solid lead are not. That is they cannot form a solid solution because their lattices are incompatible. So any solid is a mixture of solid tin + solid lead.

    On the other hand copper and nickel are miscible in all proportions in both the liquid and solid state so form an alloy at any composition in the solid. There is no eutectic in the phase diagram. The freezing and melting lines are different, as required by the phase rule.

    I am sorry I have no such information for sugars.
     

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  9. Jun 18, 2011 #8
    Interesting. I'd forgotten about crystaline structures that can contain a pair of elements in any proportion. Is the term missible really used to talk about solid phases? This is unfamiliar to me.
    Also we can have amorphous, or semi-amorphous solid states to further confuse the issue.

    Equally, I hadn't considered that there may not be a eutectic minum between two or more compounds.

    Thanks for the help.
     
  10. Jun 18, 2011 #9
    Perhaps not often since miscible really implies that you can add one to the other and stir. Solid solution is more often used. There is more than one type of solid solution. Substitutional as in the case of cupro-nickel system and insterstitial as in the case of carbon and iron.

    Some of the data came from what is IHMO the best Physical Chemistry text ever written,
    Physical Chemistry by Moore.
    He has a good chapter or three on this stuff.

    go well
     
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