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Thread: Anyone use distilled water . . .

  1. #1
    Honmei KoiCop's Avatar
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    Anyone use distilled water . . .

    for a quick calibration check on their pH meter?

    Can I assume that all distilled water should have the same pH?

    If so, what should it read?

    TIA,

  2. #2
    MCA
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    Honmei MCA's Avatar
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    If it is 100% distilled water that was not comtaminated by the container....the pH will be 7.0.

    To check my pH meter I use a 3 sample protocl using packets of calibration fluid in pH values of 7, 4, and 10. The meter can tell me how well it is tracking the range/slope from 4 to 7 to 10. When the meter can not longer handle the range within a certain percent, time to change the probe.

    Accuracy at 7 is great. But accuracy between 4 and 10 is what you want.

  3. #3
    Honmei
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    Quote Originally Posted by KoiCop View Post
    for a quick calibration check on their pH meter?

    Can I assume that all distilled water should have the same pH?

    If so, what should it read?

    TIA,
    Pure distilled water that is uncantaminated "should" have a Ph of "7". You can calibrate you Ph meter with distilled water but then recheck the claibration with multiple brands of pure distilled water to make sure that the calibration is accurate (I think you will find in most cases that there are deviations. Deependent on the amount of deviation(s), will let you know the range of accuracy.

    Steve

    Steve
    The views presented are my personal views and not that of any organization that I may belong to unless otherwise specified. [email protected]
    CKHPA

  4. #4
    Honmei KoiCop's Avatar
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    Thanks, guys. Ran 5 tests with distilled water.

    Results grouped from 6.9 to 7.2

    Guess that good enough for government work.

  5. #5
    MCA
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    Honmei MCA's Avatar
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    It is is you know what you want to test is around 7. But if the specimen in question can be much lower or higher....you need to calibrate the pH meter across a range of values....such as from 4 to 10.

  6. #6
    Honmei KoiCop's Avatar
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    From someone who was kind enough to send me an email:

    Saw your post on Bito. Here's what Norm Meck has to say about it:
    http://www.akca.org/forum/drupal/pdfs/testkit2.pdf

    a quote from page 2 says:

    The pH of absolutely pure water is undefined. Usually, distilled water will
    have a pH somewhere around 5 caused by absorption of carbon dioxide from
    the air. Just the addition of the reagent used to measure the pH will cause the
    pH of distilled water to change. We need a known checkpoint. For pH,
    dissolve two teaspoons of Sodium Bicarbonate (simple baking soda, not
    baking powder) in a cup of distilled water. A pH test of the mixture should
    read very close to 8.0.
    Don Chandler
    Member: AKCA, ZNA, KoiUSA

  7. #7
    Daihonmei PapaBear's Avatar
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    As previously stated distilled water "should" have a ph of 7.0. I assume Norm is referring to a container that has been left open to the atmosphere for an extended period of time for any acidic influence from CO2, but even then atmospheric CO2 is a tiny fraction of the whole so it would almost require enhanced exposure.

    In my own experience distilled water remains very stable for a long time. I've done a lot of lab work in days gone by and we even made our own distilled water from a source absolutely hard as stone without difficulty. It was used for calibration liquid and inert reagent mixing and always maintained a stable ph.
    Larry Iles
    Oklahoma

  8. #8
    Honmei KoiCop's Avatar
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    Thanks, Larry.

    I'm now so confused I wish I hadn't posted in the first place.

  9. #9
    Sansai
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    Why are you confused Don?
    Anyway.....I did have a jug of DW go south.....to a PH of about 6.5 I do think it was over a year old, but that's really not that long. I guess it could depend on how you store it, light???? packaging, etc.... but that's a big enough difference to make me not want to use it when a standard is what I'm going for and especially too off when talking PH. Calbration fluids are cheap enough and even though they have an expiration date, I've found them to be pretty stable.

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