All 3 (mannitol, Ideal (xylitol), and erythritol) turned the water yellow as expected in step 6.
In step 7 the mannitol and Ideal had the same drop count. The erythritol had a drop count of only 4 till it was the same shade of blue.
First I ran the test with the mannitol, using 25ml., got the drop count of 6. to the same shade. That was my base line. Second was the erythritol drop count was 5, and third was the Ideal, drop count of 6.
This was a limited run and only using 25ml.
One of the issues using the Ideal, is we don't the percentages of Xylitol, maldodextrin and sucralose in the mix. Sorry I don't have straight Xylitol.
Hope someone finds this useful.
...OR, if you want to be really accurate about it, you can use two beakers side by side and truncate the first test after you get the initial blue shade and then do the full test protocol on the second beaker to match it with. Takes more time, but it works well.
Now, what I did not tell you is that I have borates in my pool water which acts as a mild algaestat (it inhibits algae growth) AND I treat for phosphates every season (my current PO4 levels are 0ppb). Both of those conditions make my water much less "reactive" to algae, that is to say, even if algae found it's way into my water the low nutrient conditions (low PO4) and presence of the algaestat (boron levels ~ 50ppm) mean that the algae can not efficiently grow. In real terms that means that algae replication rates are slower giving chlorine much more margin to act as a sanitizer.
Thats what I was planning on doing, I guess I have to be careful to use the same amount (drop count) of BTB in each?
I've got my xylitol crystals from NuNaturals, via eBay. It contains traces of silica. Not sure if crystals or the silica will affect the test?
I'm not sure if I'm reading this correctly but unlike mannitol that complexes with borate in a 2:1 ratio, the abstract from this paper Reactions of Polyols with Boric Acid and Sodium Monoborate | SpringerLink suggests to me that xylitol complexes in a 1:1 ratio. Suggesting that I only need half the amount? Think I'll go for the full amount for now.
I've got my beakers, BTB, Taylor reagents and my speedstir arrived today. Waiting on the fancy stainless 1/8th teaspoon, ~$5 with free standard shipping from the US or $300 for express - I went for the standard.
I tried a mannitol search again in eBay and I have a winner, 100gms @ 99.9% pure for US$20 from China. So I guess I'll be able to do a side by side comparison.
Slightly off topic but it begs the question, 'why 50ppm borate?' What's your thoughts on raising it to 60 or even 70ppm? Would there be any significant benefits from a pH buffering point of view, particularly within the SWG cell?
Hi guys wondering if this Bromothymol would work? Its the 0.04%
I followed the directions above to test my borate level. My test results:
Borate: ~ 50ppm
1.) 50ml sample.
2.) 2 drops of R-0007 dechlorinates 8ppm FC.
3.) 10 drops of BTB 0.04% to get a pale blue.
4.) 9 drops of R-0009 to lower the pH and turn the sample straw yellow.
5.) 2 drops of R-0010 to get a pale blue.
6.) I used my plastic measuring spoon to mix 1/4 teaspoon mannitol powder into the sample. I don't have a speed stir. Its kind of hard to dissolve the powder by swirling by hand, plus it cleaned my spoon.
7.) 12 drops of R-0010 to turn back to the same shade of blue = 48 ppm. Since adding 50 ppm borates, I had to drain about an inch out of the pool plus had kids swimming a few days so I'd say that is pretty much on the money.
[FONT="]I've been wanting to find a usable borate drop test for a while now and have been following this borate testing thread with interest. I tried something today that I'm surprised no one has written about. I bought a pH meter and used it to perform the test with some slight changes: I don't need to neutralize the chlorine nor do I need the indicator solution. With a 50ml sample, the steps I used are:
1. Lower the pH to around 6.0 (R-0009) (I picked this number because that is where the BTB would be yellow)
2. Raised the pH (R-0010) to around 8.2 and recorded that number (the point where the BTB would be blue
3. Added the 1/4 teaspoon of Mannitol
4. While constantly stirring, I added the R-0010 drop by drop while recording the pH rise
5. When the pH reached my starting point that I recorded in step 2, I used the conversion factor of 4 x drops to get my borate ppm
The rise in pH was linear (0.1 pH change per drop) until I was approaching the end point at which time each additional drop produced a larger and larger pH change. I was hoping that the pH rise rate would be linear and a simple borate ppm calculation could be performed just knowing the starting and ending pH. Perhaps someone could come up with a formula that would account for the pH curve. I would be nice to stick two numbers into a formula and have the borate ppm calculated.
Anyway, I wanted to share this with you and see what your thoughts might be on my test method. At the very minimum I can throw away my Phenol Red and use my meter to test the pool pH. As a side note, I have played around with Clear Waters Testing's borate test kit sold on E-bay. I've had several conversation with Chris at the company and helped him find some problems with his reagents. I still have an issue getting what I think are accurate results with his procedure, but I have a couple of additional things I want to try before I contact him again.
So acid-base titrations (which is basically what the borate drop test is) are NOT linear, titration curves are always S-curves. In the case of borates, you are essentially titrating a weak acid (the boron-diol reaction) with a strong base (R-0010, sodium hydroxide). And so what you would measure using a pH probe is the pH response while adding a known volume of strong base. See this link for a quick primer on titration problems -
In the process of determining the borate concentration, you would need to plot pH as a function of titrant volume added and then you look for what is known as the equivalence point - essentially the point at which the pH curve has it's steepest slope (one can mathematically determine this with great precision by using the first and second derivatives of the pH-volume curve). Once you know the location of the equivalence point, the unknown concentration can be calculated by knowing how much titrant was added, the volume of the test solution and the pKa of the reaction. However, it is doubtful anyone would want to do this type of analysis at home because you need to have very exact quantities of solution and titrant know which requires graduated cylinders, beakers and a volumetric buret capable of measuring micro-liter volumes of titrating solutions.
The reasons why the drop based test using visual indicators is better is because -
(a) The math has already been done to equate drop count with concentrations;
(b) The visual equivalence point is easy to confirm with the BTB indicator because the transition from yellow to first baby blue is very close to the actual equivalence point
(c) There's no need to own a pH probe or spend time calibrating it or purchase anything more complicated than couple of extra test solutions. The drop test uses most everything one already has in their kit.
While I applaud your effort at home chemistry, you'd be better off just doing the test as it is outlined since it has been confirmed by multiple users of it as "accurate enough" for recreational pool purposes.