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Density of a mixture

  1. Dec 3, 2011 #1
    1. The problem statement, all variables and given/known data
    I know the density of a mixture of water and glycol. I will call that dmix. I need to find the percentage of water and the percentage of glycol in the mixture. The only other thing I know is the temp.

    2. Relevant equations


    3. The attempt at a solution

    What am unsure of is the following true

    Let x = %glycol
    Let 1-x = %water

    dmix = (x)dglycol + (1-x)dwater
  2. jcsd
  3. Dec 3, 2011 #2
    Yes, it's true. Since you have the temperature of the mixture, you can look up the densities of each component at the appropriate temperature. Then proceed.
  4. Dec 3, 2011 #3
    good. Thanks
  5. Dec 3, 2011 #4


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    Staff: Mentor

    It is NOT true. Volumes are not additive.

    For some substances - ethylene glycol included - it works quite good, but it doesn't in general. SO each time you should check if the density vs composition curve is linear - or not.
  6. Dec 3, 2011 #5
    Ok I though it might not be true. So is there another way this calc can be done with the given info?
  7. Dec 3, 2011 #6


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    Staff: Mentor

    Density table is the only sure way to go. That's how my works. Unfortunately, density table for ethylene glycol that is built into the program is limited to 60% w/w. It can be easily extended if you can find a better density table.
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