New borate drop test at piscines-apollo vs. test strip

rcy

LifeTime Supporter
Apr 25, 2009
345
Burlington, ON, Canada
Any opinions on this? I have a K2006, so I already have everything I need (except the borate kit itself). I like the idea of drops/colour changes vs. a strip, but am open to your opinions.

Would I be better off just getting the LaMotte strips? Speaking of strips, I can also get borate test strips from Hach. Anyone advise which strip is better/easier to work with?

Thanks.

The kit

http://piscines-apollo.com/cubecart/ind ... p_129.html

Instructions

http://piscines-apollo.com/docs/ap_borates_en_ins.pdf
 

JasonLion

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May 7, 2007
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The price is right :) Given that the new test is so affordable, it certainly seems worth a try.

The LaMotte strips seem to be the best of the strips. They aren't very good, but still better than every other strip. Fortunately, precision is not required on the borate test.

There is always the ProTeam Supreme Test Kit, but it is way more expensive.
 

rcy

LifeTime Supporter
Apr 25, 2009
345
Burlington, ON, Canada
Thanks for the feedback. Think I'll order this (and a magnetic stirrer...wheee) and give it a go.

Cheers.

*edit* The Piscines instructions look similar to the Pro Team test that Jason mentioned, except the Piscines kit relies on the user already having some of the reagents on hand from their own test kit (and everyone at TFP has their own kit, right? Right??)

Can anyone (chem geek??) explain how this test (the Piscines one) works. It looks like one needs reagents that would normally be used for testing alkalinity and calcium.
 

chem geek

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Mar 28, 2007
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Their test starts out adding 5 drops of Taylor R-0009 which is sulfuric acid (0.12N with a pH of 1.3). They then add a special reagent S-0009 that turns the sample yellow and appears to be an indicator dye. You then add Taylor R-0010 (used as a calcium buffer in the CH test -- really just sodium hydroxide with a pH of 13.1 -- maybe 0.12N?) until the sample turns blue. You then add S-0010 powder which turns the sample yellow if boron is present. You then titrate with Taylor R-0010 (sodium hydroxide) until the sample turns blue again. Note that at high chlorine levels, the indicator can get bleached out so one can add two drops of Taylor R-0007 (sodium thiosulfate) chlorine neutralizer prior to testing, just as with the TA test.

The pKa of Boric acid is around 9.2 so I am guessing that the pH indicator they are using in S-0009 is thymol blue which goes from yellow to blue in the range of 8.0 to 9.6 (this is its second transition; it has a first transition from red to yellow at pH of 1.2 to 2.8). [EDIT] This is probably wrong -- see this post below. [END-EDIT] This is similar to a TA test, but adding sodium hydroxide to raise the pH until a transition occurs (i.e. it's in the opposite direction). The trick is to get rid of the carbonate and CYA buffers to isolate boric acid. A standard titration method for boron uses mannitol since cis-diols form complexes with boric acid. Maybe that is what the S-0010 powder does though I don't know how. If it's a cis-diol, then it converts the boric acid into a complex that is much more acidic (pK closer to 4) that then gets titrated. So the other buffers would have been already accounted for at the first yellow-to-blue transition and the second titration is just looking at boron. This makes sense and has been reported in scientific literature (see this link, for example). Note that the reference talks about the standard determination of boron using excess mannitol.

So basically you first add acid to ensure that the pH starts out low so that the indicator dye will be yellow. You then add base to get to the transition point where the dye turns blue which is just past the transition point for just exhausting the boric acid becoming borate ion. At that point, you add mannitol which binds to the boric acid giving up hydrogen ions so is very acidic. You then titrate back up in pH by adding base until you get back to the transition point so you can therefore determine the boron level (the factor of 4.5 is for units of measurement and concentration of the base titrant).
 

chem geek

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According to this paper, the indicator dye is probably Bromocresol green. An excerpt from part of that paper is the following:

3.2. Selection of the indicator

The protonation constant of the indicator should be adequate to measure the pH changes of the solution. These changes should occur between 6 (pH of the mannitol solution) and 3.5 (the minimum pH obtained after the mannitol-borate reaction). Therefore, log KI values in the range 4.5–5.5 should be adequate.
:
Bromocresol green (log KI=4.9) was found to be the most favourable indicator.
:
[EDIT] Well, I'm wrong again apparently. The indicator is Bromothymol blue as described in this post. The scientific reference above was looking for an indicator that also worked for their spectroscopy (they don't titrate), but for a visual test a higher pH still works. [END-EDIT]

The main reason that the pH of the indicator dye needs to be lower than I originally thought is that the transition must be between boric acid (not borate ion) and the mannitol-borate complex. The reaction is the following where L(OH)2 is a polyalcohol (cis-diol) (see this paper for technical details):

B(OH)3 + 2L(OH)2 --> LO2BO2L- + 3H2O + H+

if one started with a borate ion at high pH then the pH would not drop:

B(OH)4- + 2L(OH)2 --> LO2BO2L- + 4H2O

so one must start the reaction at lower pH where boric acid is the dominant species and where the reaction acidity is able to be detected by an indicator dye.
 

rcy

LifeTime Supporter
Apr 25, 2009
345
Burlington, ON, Canada
Woot!!!! This came yesterday (and a speed stir..double Woot!!)

Anyway, the instructions were concise, the test was very easy, the colour changes were easy to spot and the price is right. Shipping was fast, too.
As long as you have a k2006 or TFT kit, you should have all the additional reagents needed to perform this test.

According to the test, my level is only 36. Off to Wal Mart for more Mule Team. I was kinda disappointed that I didn't really notice any difference after adding my Borax. Maybe it's because I'm not up near 50.
 

rcy

LifeTime Supporter
Apr 25, 2009
345
Burlington, ON, Canada
Thought I'd update this. I added three more boxes of Mule Team, and tested again. Borates are now 46ppm. So the kit definitely works as it showed the increase. I have nothing to test the accuracy, but based on how many boxes I've put in and checking poolculator.com, I would say it's accurate enough.
 

drchris66

Member
Jul 18, 2010
5
Hi folks...
Got the borate drop test kit but I'm having some issues. Seems like there's a bit of interpretation as what "...just turns blue" means. I've repeated the test several times and is seems I get a hint of blue on the 5th drop and it stays that way until about the 9th drop when it turns to the blue in the photo of the instructions. Has anyone else experienced this? According to the pool calculator I should be at about 30 based on the amount of borax I've already put in. Just want to make sure I'm not missing something.
 

chem geek

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Mar 28, 2007
12,083
San Rafael, CA USA
rcy said:
Send an email to Apollo Piscines. He'll send you back a nice picture of the blue you should be looking for.
He has the photo instructions already.

I have the drop-based test (as well as the test strips). The key to the borate drop-based test is to stop at the same point in both parts of the test. So when you see a hint of blue, add another drop and it is then a darker blue. When later on you are doing the titration portion of the test, stop at the same point. If you see a hint of blue, add another drop and if it's the darker blue then stop at that point and count even that last drop. You do not do this test in the same way as other tests in terms of "add drops until a color change and then add another drop and if no change then don't count the last drop" and you do not try and get to the exact same color as shown in the photo instructions. The indicator dye in this particular test has a broader range of pH so won't have as sharp a transition and will continue to get a little bluer. It's more about consistency between the first part of the test and the second part.

I've repeated this test multiple times choosing a different transition point and so long as I use the same type of transition point in the first and second parts of the test, I get consistent results all within one drop.
 

beezar

LifeTime Supporter
Oct 8, 2010
152
Houston, TX
so what kind of container do you use for the test? The picture shows a large pH type container and it the instructions says to have 44ml of water. I have a TF100 test kit and it doesn't the pH container isn't that type of volume. Can I just use a regular test tube, add 44ml, and use my SpeedStir magneter stirrer to do the test?
 

drchris66

Member
Jul 18, 2010
5
I did the test again, carefully watching the first transition. Staying consistent with that in the second transition gave me a reading of 27. I would say it's pretty accurate. As far as the container goes, beezar, I just measure 44mL in the 40mL flask that comes with the TF-100 (there's room above the 40 mark) and then pour it into a 1 pint mason jar.
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
They want you to use the tube that comes as part of the comparator block in the Taylor K-2xxx test kits. That tube has a white bottom and has a line for 44 ml. If you use the vial that comes with the TF-100, then put it on a white piece of paper (or white counter top) and look down into the tube. This will give you the clearest visibility for the transition and will look most like the photos in their instructions.
 

drchris66

Member
Jul 18, 2010
5
Ahh.... that might explain why I was having a hard time seeing the transitions. The mason jar is much larger so the fluid is spread out more. That would make the color less concentrated looking down into it. Thanks for the input.
 

mx702

Well-known member
Aug 2, 2010
173
MA
I'll be adding borates to my new hot tub shortly and also to my pool come spring time. I prefer to be fairly accurate in regards to testing, although I understand that high precision is not necessarily required with the addtion of borates. Nonetheless, I intend to purchase some form of borate test and I am wondering if the drop-based kit discussed here is worth the cost/time vs the strips. Anyone care to comment?
 

JasonLion

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May 7, 2007
37,880
Silver Spring, MD
For normal use, it really doesn't matter which borate test you get. The test described here is much better, but the regular test strips are perfectly fine given that there is no need, or use, for precision.