JoyfulNoise - Test for Borates

[Marcion333]

Moderator Note: Moved from this thread - What happens if I stop using chlorine

JoyfulNoise, what is the mannitol test for borates you use?

 

[JoyfulNoise]

JoyfulNoise, what is the mannitol test for borates you use?

See this thread - New borate drop test at piscines-apollo vs. test strip

Towards the end of the thread, there is a standard procedure for measuring borates. To do the test requires purchasing mannitol powder and bromothymol blue indicator. I also suggest you find a 50mL pyrex beaker and you use a speedstir to do the test. All other reagents can be found in your K-2006 kit and the other stuff can be bought on Amazon. The test is a bit tricky to get right because it requires matching some fairly light colors (blues & yellow).

Matt

 

[Patrick_B]

Out of curiosity Matt, can you add more Bromothymol Blue to make the endpoint more vivid, or can it skew results?

 

[JoyfulNoise]

Out of curiosity Matt, can you add more Bromothymol Blue to make the endpoint more vivid, or can it skew results?

Yes, you can. The BTB is just an indicator dye so, in principle, it plays no part in the reaction between the borates and mannitol. The product on Amazon is the highest possible concentration of BTB possible in water (BTB has fairly low solubility), so you do need to use a number of drops just to get the color to show. Also, that particular product is in a very lousy dropper bottle, more like a dribble bottle so it's actually quite hard to get uniform, well formed droplets from it. Even so, I have played with the droplet count and found no effect on the results when adding extra drops.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[ewkearns]

I also suggest you find a 50mL pyrex beaker and you use a speedstir to do the test.

In the interest of keeping everything I can in my test kit non-breakable, I opted for this:

https://www.taylortechnologies.com/products_Partinfo.asp?MarketID=1&ReplacementPartID=2013

It fits in the K-2006C kit perfectly, but is a little tipsy on the Speedstir.

Also, items from the original thread had gone out of stock, but could still be bought on Amazon from different suppliers.

I found the LaMotte test strips nearly useless, because they had a rainbow of hues progressing from the perimeter moving inward towards the center. I always felt like I was just guessing at a value. I like the Bromothymol/Mannitol test because it gives a definitive numerical value.

 

[JoyfulNoise]

Taylor does actually make a boron test kit. The only problem is the range is quite low (0.2 or 0.5 ppm/drop of titrant with a 15ppm upper limit and so would require sample dilution), its a fairly complicated test protocol (14 steps with sample prep and syringe filtration) AND it costs ~$200.

But I agree, the strips are pretty bad especially since they are time sensitive as the color slowly fades and changes.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[Patrick_B]

Yes, you can. The BTB is just an indicator dye so, in principle, it plays no part in the reaction between the borates and mannitol. The product on Amazon is the highest possible concentration of BTB possible in water (BTB has fairly low solubility), so you do need to use a number of drops just to get the color to show. Also, that particular product is in a very lousy dropper bottle, more like a dribble bottle so it's actually quite hard to get uniform, well formed droplets from it. Even so, I have played with the droplet count and found no effect on the results when adding extra drops.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

I figured it was the same as anything else. Methyl Orange or whatever, just want certain. I always overload on these indicators. I like strong, vivid endpoints.

 

[JoyfulNoise]

Unfortunately the test is not a true endpoint titration. In the last step, you are adding drop to achieve the same color/shade of blue that you saw in the first part of the test before adding the mannitol (which turns the solution a pale yellow). So, in practice, you can over titrate the end point and get a darker blue. This is what makes the test a little tricky - you have to try to remember what blue shade you are looking for. Thankfully the transition from yellow to blue is well defined enough so that you're not stuck with some mixture of color in between drops.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[ewkearns]

Also, that particular product is in a very lousy dropper bottle, more like a dribble bottle so it's actually quite hard to get uniform, well formed droplets from it.

Yeah, it is! It appears to be a controlled dropper tip, because it does accurately and reliably dispense 40 µl drops (à la Taylor). However, the orifice is so large it wants to squirt, rather than take it slow and easy when forming a drop. The fact that it is LDPE, rather than HDPE, makes the bottle squishy, anyway. I was a little surprised to find it wasn't the standard 50 µl tip. It might be worth transferring it to a more reliable bottle.

 

[JoyfulNoise]

Yeah, it is! It appears to be a controlled dropper tip, because it does accurately and reliably dispense 40 µl drops (à la Taylor). However, the orifice is so large it wants to squirt, rather than take it slow and easy when forming a drop. The fact that it is LDPE, rather than HDPE, makes the bottle squishy, anyway. I was a little surprised to find it wasn't the standard 50 µl tip. It might be worth transferring it to a more reliable bottle.

That's actually a great idea. The bottle itself, 60mL, is a HUGE quantity. Transferring to a smaller, more reliable dropper bottle would be best.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[ewkearns]

If you do, don't make the same mistake I was just about to make.... I just grabbed an old bottle, pulled the label off, and proceeded to pull the dropper tip out. Of course, the first empty bottle I picked up would have an R-0013 tip. Taylor makes two tips, one is clear and is a controlled dropper tip, the other is white and is not controlled. I had to swap tips to make sure I didn't have the same issues with another bottle. IOW, you want the controlled tip.

 

[JoyfulNoise]

Any vendors that sell them? I worked in a chemical lab - never mix old and new!!


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[ewkearns]

Any vendors that sell them? I worked in a chemical lab - never mix old and new!!

I agree, but thus far, I haven't found a vendor carrying 40 µl tips that fit round or cylindrical bottles over about .5 ounce. I prefer the cylinder, because the 2 oz. Boston Rounds just don't fit in but one compartment of my kit.

 

[Patrick_B]

I worked in a chemical lab-

Lab Rat!!!! :jocolor:

- - - Updated - - -

Unfortunately the test is not a true endpoint titration. In the last step, you are adding drop to achieve the same color/shade of blue that you saw in the first part of the test before adding the mannitol (which turns the solution a pale yellow). So, in practice, you can over titrate the end point and get a darker blue. This is what makes the test a little tricky - you have to try to remember what blue shade you are looking for. Thankfully the transition from yellow to blue is well defined enough so that you're not stuck with some mixture of color in between drops.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

And no wonder you say what you did about recommending it. Sheesh.

 

[ewkearns]

I agree, but thus far, I haven't found a vendor carrying 40 µl tips that fit round or cylindrical bottles over about .5 ounce. I prefer the cylinder, because the 2 oz. Boston Rounds just don't fit in but one compartment of my kit.

Found an answer! Taylor sells bottles, tips, and white caps. As far as I can determine, their dropper tips are specially made either by or for them and are a special item..... and (for what they are) they are quite pricey....

 

[JoyfulNoise]

Interesting. Thanks.

Yes, I've been looking online and all of the bottle fitments (that's what they are technically called....weird) and caps are sold in bulk, ex quantity 1000 for $400. So that's not really an option.

Hmmmm....my next purchase may include a dropper bottle...


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[AUSpool]

I was thinking that a borate buffer would be a good thing for me but I also think it is important to only add something that I can test for. I had intendened to use the strips but reading the above they sound a bit unconclusive and the test as just described is not for me. So maybe borates is not for me but I've just ordered 9kg of boric acid that assuming I have 0ppm borates now, should bring my pool up to 50ppm.

The test strips are yet to be ordered. Which way do borates usually drift to, up, down or remain stable? With five years of records I have always had to add CH, AKl and CYA. Having added a solar heater my evaporation has increased by 15-25% so this may change.

If I go ahead and add the boric acid can I gain some pH stabilisation benefit for the short term and slowly let it deplete without any more additions?

 

[JoyfulNoise]

Borates act like salt and CH, they only decrease when water is removed and fresh water is added back in. So if you can determine what percentage change in CH you typically observe over a season, then your borates should roughly track that same pattern of change.

Strips will work to get you in the ballpark as that is what I used before I learned how to do the mannitol test. Many people that use borates just use strips and they are perfectly happy with the results. There's no magic range for borates. For me, my pool needs them to be above 35ppm for best results and I try to keep them no higher than 50ppm or so. If I accidentally hit 60ppm, no big deal.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[JoyfulNoise]

Actually, upon further reflection, borates may or may not track well with salt or CH. Municipal water supplies can add both salt and CH to your pool depending on how well treated the water is. Salinity is often fairly low but CH can be quite high depending on what area of the country (or world!) you live in. Be that as it may, borates will not be added to your pool by any input water source so the driving force for borate concentration will always be to lower it. The rate at which it goes down will be entirely dependent on how much of the pool water, aside from evaporation, is removed and replaced during the season.