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Thread: Is all pH indicator solution the same?

  1. Back To Top    #1

    Join Date
    Jul 2007
    Sahuarita, AZ

    Is all pH indicator solution the same?

    I ran out of my red pH indicator solution from my TF-100 kit. I have a crappy kit that was provided from the PB that has a bottle of pH indicator solution. Both the TF-100 and other kit bottles say the solution is 'phenol red'. Is all phenol red the same or is it possibly a different strength from the other kit. I could just take both kits out to the pool but I'd rather just put the full bottle of phenol red from the other kit into the TF-100 box. I ask because the mixing chamber in the other kit seems a lot larger than the one in the TF-100 so 5 drops would dilute more in the other kit. But perhaps the color shades on the sides are just calibrated accordingly.

    Any thoughts? I know I could just order refills, but I'm lazy and cheap.

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  2. Back To Top    #2

    Join Date
    Jan 2009
    Cupertino, CA

    Re: Is all pH indicator solution the same?

    I know they're not all the same, Taylor makes two: the R-0014 you got in the K-1000 that's in the TF100 kit, and then the R-0004 (I think) that comes with the K-2006. They are tuned for different size water samples, although my understanding is they are both founded on phenol red. You should use the sample size specified by the kit that the stuff came from.

    I suspect that the colors do work out the same; with my K-1000 next to my first cheapo kit, the color blocks look comparable.
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  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Is all pH indicator solution the same?

    They are not the same, though you could get away with using it if you really want to. There are two things to keep in mind. First, it probably isn't the same strength. Compare the size of the two viewing vials and scale the number of drops accordingly. For example, if the TF100s vial is half as large, you use half as many drops. The other issue is compensation for high FC levels. Many cheaper kits don't buffer their PH reagent against FC nearly as much and therefor give inaccurate results at much lower FC levels.
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  4. Back To Top    #4

    Re: Is all pH indicator solution the same?

    The good news is that phenol red will produce the same color changes for different pH levels. However if you are using the wrong size sample the color might be too intense or faded to match the comparator block.
    The solution to this dilemma? Just look at the color itself and not how faded or deep it is....
    If it is:
    yellow your pH is 6.8 or lower
    yellow orange it's 7.0
    orange 7.2
    red oragne 7.4
    pure red 7.6
    pinkish red 7.8
    blue red 8.0 or higher.

    It takes a bit ot experience with reading your pH test to be able to do this but if you look at the color (but not the intensity) whenever you test your pH soon you will be able to recognise the colors without the comparator, even if theyare faded from too big a sample size or very intense from too small a sample size.

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