New borate drop test at piscines-apollo vs. test strip
- Thread starter rcy
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- May 23, 2015
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It's not a bother I apologize if you felt I was marginalizing your efforts.
If you want to use your pH probe to do the work then I suggest you add the BTB indicator to the solution and look for the visual change of yellow to blue and what pH that corresponds to. That is the pH value you want to hit, not some arbitrary high value. But please note that the pH transition can shift depending on the TA of the solution. So you need to make sure your pool water parameters are reasonably close with every test or else you'll need to recalibrate what pH value you're looking for.
HOO
0
I understand what you are saying, but let me explain my thoughts a little further. I am not picking an arbitrary high value. I am using a value around 8.2 pH which, according to a BTB Color Scale, is the point where BTB turns blue. Most likely the value will not be exactly 8.2 because when adding one more drop of R-0010 prior to reaching 8.2 the value will probably overshoot to 8.3 or 8.4. Now I record that value. Isn''t this is the same as your blue starting point? Knowing this value, to me, is more accurate than trying to remember the shade of blue. When counting drops and titrating back to to this end point all I have to do is watch the pH meter and stop when I reach that value I recorded. If one drop overshoots the recorded value, then I use the number of drops up to that point, before the overshoot, and add 2 to the calculated ppm. 2 is half a drop. I don't see how this procedure differs from using an indicator solution unless your saying that TA can affect the BTB blue end point. In that case, the BTB color would not be a true indicator of a pH value and the color scale charts would all be wrong.
Assuming my above logic is valid, why buy and store a somewhat large bottle of indicator solution that you only use few drops from a year? Reading a display is easier than remembering a shade of blue. You can get some pH pens for less than the cost of BTB. Calibration is not a deterrent, its easy and fast. Plus there is no need to use up your R-0007. Also a pH pen has other uses, testing the pool pH instead of using Phenol Red and a color chart, for example.
Assuming my above logic is valid, why buy and store a somewhat large bottle of indicator solution that you only use few drops from a year? Reading a display is easier than remembering a shade of blue. You can get some pH pens for less than the cost of BTB. Calibration is not a deterrent, its easy and fast. Plus there is no need to use up your R-0007. Also a pH pen has other uses, testing the pool pH instead of using Phenol Red and a color chart, for example.
- May 23, 2015
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Your thinking is correct, my explanation was not clear - the color transition doesn't change with TA as you state, simply the number of drops you might need to use to move between color transitions. I believe user smackdab did some tests of how much R-0009 it took to lower the pH relative to different levels of TA. I'm not sure if he also did a similar test for how many drops of R-0010 it took to raise TA but we could always ask for his input. Thinking about it further, it shouldn't matter much either way and likely has no impact on the test as the change in pH is entirely due to borate-diol reaction. I could go check some numbers in a spreadsheet later today when I'm at my Mac but I suspect the impact of TA at levels found in pools is minimal at best.
If you want to check your testing then the answer is simple - you should get the BTB indicator dye and calibrate your testing to that to prove that it works as you say it will. In theory it should but it's always up to the tester to prove that their new protocol works properly and the way to do that is with a side-by-side comparison.
As for me, testing with color indicators is fast and easy and hasn't really been an issue. A bottle of the BTB indicator is quite large and costs around $20. One uses more than a few drops with it - I use about 1mL or so of indicator each time, so storage/shelf-life is not an issue (it's a very stable chemical). But, given the bottle size, that represents hundreds of tests. The amount of R-0007 used is trivial - around one or two drops and I'm still working on the same 0.75oz bottle of R-0007 I purchased many years ago and that is with regular TA testing. To me, pH pens are nice but an over-complication in most cases. I know many on TFP like to have them to help reassure themselves that they are seeing the appropriate colors in a pH test but they are not necessary for pool care except in the odd circumstance of true color blindness (as opposed to color discrimination issues). Cheap pH pens typically can not be calibrated and don't usually last more than one year. More expensive pH probes can be calibrated (typically two points) and will last a little but longer if they are properly cared for. Bottles of BTB and phenol red will last many years and never need calibration. So since one of the main objectives of pool testing is to keep things simple for the user, color indicators are usually best.
Please go ahead and compare your test results with the standard BTB test and I, for one, would be interested in seeing the results.
If you want to check your testing then the answer is simple - you should get the BTB indicator dye and calibrate your testing to that to prove that it works as you say it will. In theory it should but it's always up to the tester to prove that their new protocol works properly and the way to do that is with a side-by-side comparison.
As for me, testing with color indicators is fast and easy and hasn't really been an issue. A bottle of the BTB indicator is quite large and costs around $20. One uses more than a few drops with it - I use about 1mL or so of indicator each time, so storage/shelf-life is not an issue (it's a very stable chemical). But, given the bottle size, that represents hundreds of tests. The amount of R-0007 used is trivial - around one or two drops and I'm still working on the same 0.75oz bottle of R-0007 I purchased many years ago and that is with regular TA testing. To me, pH pens are nice but an over-complication in most cases. I know many on TFP like to have them to help reassure themselves that they are seeing the appropriate colors in a pH test but they are not necessary for pool care except in the odd circumstance of true color blindness (as opposed to color discrimination issues). Cheap pH pens typically can not be calibrated and don't usually last more than one year. More expensive pH probes can be calibrated (typically two points) and will last a little but longer if they are properly cared for. Bottles of BTB and phenol red will last many years and never need calibration. So since one of the main objectives of pool testing is to keep things simple for the user, color indicators are usually best.
Please go ahead and compare your test results with the standard BTB test and I, for one, would be interested in seeing the results.
The only reason I calculated the drops of R-0009 needed is so one can do the borate test starting at the same pH level of ~6.0 for consistancy, which is a yellow color with the dye. My TA was 60, now it is 90 because of my high TA fill water so now I can consistantly test starting from 6.0 by adjusting the amount of R-0009. I find it easier to go through the color transition right back to the same shade of blue for some reason. Maybe it's just my eyes, not sure. If you want to use this information, I will provide it.
These are the drops of R-0009 needed to lower the pH to 6.0 in a 50 ml water sample:
TA 50: 7 drops
TA 60: 8 drops
TA 70: 9 drops
TA 80: 10 drops
TA 90: 11 drops
TA 100: 12 drops
TA 110: 13 drops
TA 120: 14 drops
TA 130: 15 drops
TA 140: 16 drops
For a 25 ml water sample, use half the amount shown.
These are the drops of R-0009 needed to lower the pH to 6.0 in a 50 ml water sample:
TA 50: 7 drops
TA 60: 8 drops
TA 70: 9 drops
TA 80: 10 drops
TA 90: 11 drops
TA 100: 12 drops
TA 110: 13 drops
TA 120: 14 drops
TA 130: 15 drops
TA 140: 16 drops
For a 25 ml water sample, use half the amount shown.
I did not figure for that. Keep in mind I'm not a chemistry major. As for the drops of R-0009, I used Pool Math, some extra calcuations and head scratching, and 0.437% HCl as in this post to figure up the pH drop.
For a little better explanation: I used the "metric system", starting pH 7.6, borates 50 ppm, various TA levels, target pH of 6.0 in the calculations, and a few other tweaks such as exagerated pool gallons (to get small numbers), 20 drops per ml, and multiplying 31.45% MA by 71.968 to get 0.437%MA.
Last edited:
- May 23, 2015
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So I had some time to some further research and I think if you can run a few careful tests of your setup with the pH probe, you should be able to get reasonably good agreement. This Link to an old paper shows that if one uses a sufficiently high ratio of mannitol to boric acid concentrations, then the error in the titration, i.e., the difference in pH between the equivalence point and the plateau of the pH rise, should be sufficiently small enough that you can basically assume they're equivalent.
I would simply suggest you try to chart up a few titration curves to see if you are getting a sufficiently steep slope at the equivalence point and then you can simply assume your test is working correctly.
HOO
0
HOO
0
While waiting for my BTB to arrive, I did some testing using Phenolphthalein as the indicator. The results are interesting. When I get the data cleaned up and readable I'll post it along with my BTB data. One thing nice about PHPH is it's sudden change from clear to pink. Easy to spot unless you manage to hit the pH where it just begins to turn a very faint pink (one more drop and you get a vivid pink.) Only problem is it remains clear in an acid solution so when initially lowering the pH to neutralize the carbonate alkalinity you don't see a color change. I think, however, by using smackdab's R-0009 drop tabulation, or a pH probe, suitable results can be gotten. Speaking of pH pens, looking on Amazon, some of the less expensive pens have pretty good ratings.
More later.....
More later.....
- May 23, 2015
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One technique uses methyl orange indicator (yellow at high pH, transitions to red at a pH of 3.1) to determine the lower pH transition and then phenolphthalein to see the upper transition. So you'd have a mix of yellow and pink which will produce a shade of orange. The need to use MO arose from the fact that boric acid stock solutions would often be prepared from mixing borax with water and then acidifying with acid. One needed to determine how much acid to use to convert all of the borate to boric acid.
Look forward to your results.
Look forward to your results.
HOO
0
The conversation regarding piscines-apollo drop test and test strips basically ended on page 4. The discussion changed to devising a working drop test among TFP members. Why is this conversation off topic now? If you want to move it to a new thread, it's fine with me, but I was just curious about your view point. Incidentally I may have uncovered a possible issue with the current BMB test. I have to plot some data first and then I'll post the results. I'm probably wrong but I want some feed back on what I am coming up with.
It's just my opinion, but the procedure you're proposing has nothing to do with the original test, it's an alternative test procedure, following a different procedure from the original posting. It should get it's own topic/discussion. I mean no offense, but the proper recognition that your process deserves.
- May 23, 2015
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I would rather the posts stay here. This thread has a certain following to it and if HOO has some relevant info to the test itself, I'd rather it stay here so those that are subscribed can see it.
HOO
0
These tests were done in my kitchen, accuracy is not guaranteed. I am not a chemist and could be way off base with all of this data. I am, however, quite anal about my water chemistry, and I do believe they are fairly accurate and provide some useful information when testing for borate using a drop test. Sorry if I made this write-up too long, but I want to give you all of the details of my experiment. These are my interpretations and I welcome criticisms and comments.
I am providing five titration curves. One using a Phenolphthalein indicator, two using a Bromothymol Blue indicator, and three using a Ph Meter and beginning the test at different pH levels, namely: 7.4, 8.3 and 8.9. It will be noted that the starting pH level has a effect on the curve shape and the endpoint interpretation.
The tests were done using a borate solution of approximately 50 ppm. All tests used the same solution. The results of the tests tend to show the value to be around 45 to 48 ppm which I accept as being a correct.
All tests involved lowering the pH to neutralize any carbonates as spelled out in the TFP procedure. Then, in the BTB and PHPH tests, the pH was raised to the indicator's color point with R-0010. In the pH Meter's test, the solution's pH was then raised to the desired pH, i.e. 7.4, 8.3, or 8.9 with R-0010. Mannitol was add and the solution was titrated using R-0010 until the proper color or the starting pH was reached. In the case of the pH Meter tests, this usually resulted in an overshoot of one drop. The drops were multiplied by four to find the final ppm value.
Examining the three pH Meter curves you will note that the 7.4 pH curve is somewhat flat and results in a reasonable ppm between 40 and 44. The 7.4 pH endpoint is lower on the curve than it should be and reflects the possibility of an inaccurate value. Lower pH starting points can be deemed to result in more and more inaccuracy.
The 8.9 pH curve, on the other hand, shows a value under 32 ppm and is not accurate at all.
The 8.3 pH curve looks good. It has a value between 44 and 48 ppm and an endpoint about where it should be.
Now for the 7.6 pH BTB curve. Determining the point where the solution first became blue was subjective for me. The graph was based on the point where I saw pale blue and the solution had a pH of 7.6. This BTB curve is similar to the previous 7.4 pH curve.
Repeating the test, I added an extra drop of R-0010 when I reached the first blue point resulting in a 8.4 pH. This BTB curve has a good shape and appears quite accurate with a ppm of 48.
The PHPH test was started with a pH of 8.6 which is just shy of the 8.7 pH faint pink color endpoint. The curve is well defined and returns a value of 44 ppm. The 8.7 endpoint is where it should be on the curve. Note how this curve and the previous 8.3 pH curve are quite similar. One problem with using PHPH is that it cannot be of any use when lowering the pH initially to neutralize carbonates since it remains colorless.
In summary I think all three methods can give acceptable results, but extra precautions should be used when testing with BTB or pH Meter. These are the caveats are below.
I don't know at which pH point the carbonates are eliminated. Using the pH Meter, I lowered the pH to 6.0 or below. When going by the BTB color, I could get a yellow reading as high as 6.9. It would take 8 more drops of R-0009 to reach 6.0. Is this an issue? I don't know, comments needed.
The pH starting point of the test is critical. With BTB, I noticed a blue hue with a pH as low as 7.6 and you can see the results are questionable. In addition, the reaction between the R-0010 and the test solution's color change is very slow, even with constant stirring. If you don't wait for the color change to stabilize before adding the Mannitol, the results will be incorrect. I feel that a starting pH of 8.3 to 8.7 provides the best results. I also suggest when the first stable blue color is noticed add one more drop of R-0010. If the color remains the same, you are good to go. If the color changes add one more drop.
In my test solution, one drop of R-0010, added to a pH of 7.6, raised it to 8.2, another drop to 8.5 and another to 8.7. A fairly low increase per drop. I assume, however, when testing borate solutions with a lower ppm, the increase per drop would be greater. Personally, when using the BTB test, I will always add at least one more drop.
OK, questions, comments, pitchforks and torches anyone?
I am providing five titration curves. One using a Phenolphthalein indicator, two using a Bromothymol Blue indicator, and three using a Ph Meter and beginning the test at different pH levels, namely: 7.4, 8.3 and 8.9. It will be noted that the starting pH level has a effect on the curve shape and the endpoint interpretation.
The tests were done using a borate solution of approximately 50 ppm. All tests used the same solution. The results of the tests tend to show the value to be around 45 to 48 ppm which I accept as being a correct.
All tests involved lowering the pH to neutralize any carbonates as spelled out in the TFP procedure. Then, in the BTB and PHPH tests, the pH was raised to the indicator's color point with R-0010. In the pH Meter's test, the solution's pH was then raised to the desired pH, i.e. 7.4, 8.3, or 8.9 with R-0010. Mannitol was add and the solution was titrated using R-0010 until the proper color or the starting pH was reached. In the case of the pH Meter tests, this usually resulted in an overshoot of one drop. The drops were multiplied by four to find the final ppm value.
Examining the three pH Meter curves you will note that the 7.4 pH curve is somewhat flat and results in a reasonable ppm between 40 and 44. The 7.4 pH endpoint is lower on the curve than it should be and reflects the possibility of an inaccurate value. Lower pH starting points can be deemed to result in more and more inaccuracy.
The 8.9 pH curve, on the other hand, shows a value under 32 ppm and is not accurate at all.
The 8.3 pH curve looks good. It has a value between 44 and 48 ppm and an endpoint about where it should be.
Now for the 7.6 pH BTB curve. Determining the point where the solution first became blue was subjective for me. The graph was based on the point where I saw pale blue and the solution had a pH of 7.6. This BTB curve is similar to the previous 7.4 pH curve.
Repeating the test, I added an extra drop of R-0010 when I reached the first blue point resulting in a 8.4 pH. This BTB curve has a good shape and appears quite accurate with a ppm of 48.
The PHPH test was started with a pH of 8.6 which is just shy of the 8.7 pH faint pink color endpoint. The curve is well defined and returns a value of 44 ppm. The 8.7 endpoint is where it should be on the curve. Note how this curve and the previous 8.3 pH curve are quite similar. One problem with using PHPH is that it cannot be of any use when lowering the pH initially to neutralize carbonates since it remains colorless.
In summary I think all three methods can give acceptable results, but extra precautions should be used when testing with BTB or pH Meter. These are the caveats are below.
I don't know at which pH point the carbonates are eliminated. Using the pH Meter, I lowered the pH to 6.0 or below. When going by the BTB color, I could get a yellow reading as high as 6.9. It would take 8 more drops of R-0009 to reach 6.0. Is this an issue? I don't know, comments needed.
The pH starting point of the test is critical. With BTB, I noticed a blue hue with a pH as low as 7.6 and you can see the results are questionable. In addition, the reaction between the R-0010 and the test solution's color change is very slow, even with constant stirring. If you don't wait for the color change to stabilize before adding the Mannitol, the results will be incorrect. I feel that a starting pH of 8.3 to 8.7 provides the best results. I also suggest when the first stable blue color is noticed add one more drop of R-0010. If the color remains the same, you are good to go. If the color changes add one more drop.
In my test solution, one drop of R-0010, added to a pH of 7.6, raised it to 8.2, another drop to 8.5 and another to 8.7. A fairly low increase per drop. I assume, however, when testing borate solutions with a lower ppm, the increase per drop would be greater. Personally, when using the BTB test, I will always add at least one more drop.
OK, questions, comments, pitchforks and torches anyone?
- May 23, 2015
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HOO,
No pitchforks here. I will have to very slowly read your post to comment. But, I want to say I misunderstood your PM and told you to use PDFs. That was wrong. My apologies. Can you please repost your graphs using JPG. If you have trouble posting images, contact Leebo, the site admin, and he'll get them uploaded to TFP with proper IMG codes for you to cut and paste into your post.
Thanks. And EXCELLENT WORK!!
PS - Dropping pH is not to remove carbonates. That is wrong and I should go back and make sure that is edited out. Dropping pH is to ensure that all boron species are in the form of boric acid, B(OH)3. Otherwise the mannitol-boron complex formed will not produce an acid proton but simply a water molecule.
No pitchforks here. I will have to very slowly read your post to comment. But, I want to say I misunderstood your PM and told you to use PDFs. That was wrong. My apologies. Can you please repost your graphs using JPG. If you have trouble posting images, contact Leebo, the site admin, and he'll get them uploaded to TFP with proper IMG codes for you to cut and paste into your post.
Thanks. And EXCELLENT WORK!!
PS - Dropping pH is not to remove carbonates. That is wrong and I should go back and make sure that is edited out. Dropping pH is to ensure that all boron species are in the form of boric acid, B(OH)3. Otherwise the mannitol-boron complex formed will not produce an acid proton but simply a water molecule.
- May 23, 2015
- 24,403
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Link please. It could be very old OR it could be a soil boron tester which has a max limit of 2ppm Boron.