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Testing for plastic in water

  1. Feb 7, 2019 #1
    On wikipedia (https://en.wikipedia.org/wiki/Iron(III)_chloride) it says:
    The ferric chloride test is a traditional colorimetric test for phenols, which uses a 1% iron(III) chloride solution that has been neutralised with sodium hydroxide until a slight precipitate of FeO(OH) is formed.[26] The mixture is filtered before use. The organic substance is dissolved in water, methanol or ethanol, then the neutralised iron(III) chloride solution is added—a transient or permanent coloration (usually purple, green or blue) indicates the presence of a phenol or enol.

    So what materials do I need? Ferric chloride (saw it for sale on Amazon) and Sodium Hydroxide (I can check). Then how do I exactly neutralise it to satisfy the conditions and what do they mean by filter. Remove solids? With what?

    I have a physics background but almost no chemistry background...
  2. jcsd
  3. Feb 7, 2019 #2

    jim mcnamara

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    Staff: Mentor

    1. pH test strip kit - the one meant for testing soils will work.
    2. filter paper circles - used to filter out solids
    3. funnel - line the inside of the funnel with moistened filter paper, folded so the it lays mostly flat against all the way round the inside of the funnel
    4. some small glasses
    5. Small cheapo eye dropper
    6. distilled water; see comment below
    7. some glass stirring rods - stainless steel spoons are okay too. Obviously plasticware is not okay.

    Use distilled water only - in the grocery store in the laundry section. For ironing clothing (or playing chemist).
    FeCl2, ferric chloride dissolved in water:
    1% sol'n = 1g FeCl3 dissolved in 95g (95ml). After it is dissolved add quantity sufficient of water to make 100ml.

    Make a 5% sol'n by weight of NaOH in water, 20ml H2O using same technique. Note NaOH is nasty (it is lye), so use eye protection.

    Drop-wise (eyedropper), place NaOH sol'n into Iron sol'n, stir, if you see slight cloudiness, check with test strip to see the pH is at or above 7. Continue dropping and stirring and testing until you get pH=>7.0

    Remove the cloudiness from the iron sol'n by SLOWLY pouring the the iron sol'n through the filter paper. Pitch the paper, keep the iron sol'n.

    Wash out the eyedropper, to use in your colorimetic tests

    Run your tests.
  4. Feb 7, 2019 #3
    Thank you! I think that covers everything. I guess the other question on my mind is how to map color to concentration (ppm), at least roughly, but I will look around.

    Edit: I think one way is to take a control sample of water I consider "clean" and see if there is a major difference.
  5. Feb 7, 2019 #4

    jim mcnamara

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    Staff: Mentor

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