TF-100 Test Kit Reagents

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KevDawg673

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Aug 1, 2016
22
Clay, NY
Hey all,

I'm relatively new here and I am very interested in how the reagents for the TF-100 test kit work. I have a Bachelor's degree in Chemical Engineering so am familiar with how things are mixing together when the tests are performed, I'm just very curious what specific chemicals are used and the mechanism of action. I'm not even sure if it would be possible to tell me; are the reagents kept a secret? Just trying to educate myself a little further!!
 
I can answer in detail later tonight. But basically here's the run down -


FC/CC Test - Uses DPD dye for a pink color and ferrous ammonium sulfate as the titrant. Dye is oxidized by FC to a Wurster dye to turn pink and the FAS converts it back. Potassium iodide is then added which causes the CC's to oxidize the dye and then more FAS is added to titrate. Hach has a very good PDF on the reactions.

TA - this is just a titration of the alkalinity in the pool water. Basically a specialty dye is added to the water sample with a green/red transition at a pH lower than 4.5. Sulfuric acid is the titrant where each drop neutralizes approximately 10ppm of alkalinity (carbonates, borates and cyanurates). Once the pH drops below 4.5, the test is complete.

pH - just phenol red indicator with a mix of dechlorinating chemicals

CYA - melamine is the R-0013 reagent. It reacts with CYA at low pH to form a melamine cyanurate precipitate (actually a hydrogen bonded melamine cyanuric acid adduct). The test is basically a crude turbidity measurement.

CH - Eriochrome Black dye is the indicator. R-0010 is just sodium hydroxide to reduce the magnesium concentration (by forming magnesium hydroxide). The R-0012 (eriochrome black) reacts with divalent metals (Ca2+) to form a reddish-pink complex. The titrant is a mixture of EDTA and another chelant that more strongly attracts the calcium ions. Once all of the calcium is stripped form the eriochrome black, the dye changes from reddish-pink to blue.

Salt - Mohr's argentometric titration. Potassium chromate is the yellow-red/brown indicator. Silver nitrate is used to precipitate out silver chloride. Once all of the chloride is removed from the solution, the silver reacts with the chromate to form a reddish-brown silver chromate compound.

Those are there major tests. They can be found in just about any quantitative chemistry or solutions chemistry textbook you might have access to.
 
JoyfulNoise said:
I can answer in detail later tonight. But basically here's the run down -


FC/CC Test - Uses DPD dye for a pink color and ferrous ammonium sulfate as the titrant. Dye is oxidized by FC to a Wurster dye to turn pink and the FAS converts it back. Potassium iodide is then added which causes the CC's to oxidize the dye and then more FAS is added to titrate. Hach has a very good PDF on the reactions.

TA - this is just a titration of the alkalinity in the pool water. Basically a specialty dye is added to the water sample with a green/red transition at a pH lower than 4.5. Sulfuric acid is the titrant where each drop neutralizes approximately 10ppm of alkalinity (carbonates, borates and cyanurates). Once the pH drops below 4.5, the test is complete.

pH - just phenol red indicator with a mix of dechlorinating chemicals

CYA - melamine is the R-0013 reagent. It reacts with CYA at low pH to form a melamine cyanurate precipitate (actually a hydrogen bonded melamine cyanuric acid adduct). The test is basically a crude turbidity measurement.

CH - Eriochrome Black dye is the indicator. R-0010 is just sodium hydroxide to reduce the magnesium concentration (by forming magnesium hydroxide). The R-0012 (eriochrome black) reacts with divalent metals (Ca2+) to form a reddish-pink complex. The titrant is a mixture of EDTA and another chelant that more strongly attracts the calcium ions. Once all of the calcium is stripped form the eriochrome black, the dye changes from reddish-pink to blue.

Salt - Mohr's argentometric titration. Potassium chromate is the yellow-red/brown indicator. Silver nitrate is used to precipitate out silver chloride. Once all of the chloride is removed from the solution, the silver reacts with the chromate to form a reddish-brown silver chromate compound.

Those are there major tests. They can be found in just about any quantitative chemistry or solutions chemistry textbook you might have access to.
Click to expand...

That's all wrong...there's little elves in those bottles that change the colors!
 
pinguy said:
Question about this ....

The Taylor K2006/c comparator uses a 45ml sample, and the midget comparator in the K1001 uses a much smaller sample, yet you use the same amount of Phenol Red. How does that work?
Click to expand...

The phenol red reagents are different. For the 2000series comparator block you use the R-0004 phenol red indicator. For the midget comparator you use the R-0014 phenol red. The acid/base demand reagents are different as well.
 
JoyfulNoise said:
I can answer in detail later tonight. But basically here's the run down -


FC/CC Test - Uses DPD dye for a pink color and ferrous ammonium sulfate as the titrant. Dye is oxidized by FC to a Wurster dye to turn pink and the FAS converts it back. Potassium iodide is then added which causes the CC's to oxidize the dye and then more FAS is added to titrate. Hach has a very good PDF on the reactions.

TA - this is just a titration of the alkalinity in the pool water. Basically a specialty dye is added to the water sample with a green/red transition at a pH lower than 4.5. Sulfuric acid is the titrant where each drop neutralizes approximately 10ppm of alkalinity (carbonates, borates and cyanurates). Once the pH drops below 4.5, the test is complete.

pH - just phenol red indicator with a mix of dechlorinating chemicals

CYA - melamine is the R-0013 reagent. It reacts with CYA at low pH to form a melamine cyanurate precipitate (actually a hydrogen bonded melamine cyanuric acid adduct). The test is basically a crude turbidity measurement.

CH - Eriochrome Black dye is the indicator. R-0010 is just sodium hydroxide to reduce the magnesium concentration (by forming magnesium hydroxide). The R-0012 (eriochrome black) reacts with divalent metals (Ca2+) to form a reddish-pink complex. The titrant is a mixture of EDTA and another chelant that more strongly attracts the calcium ions. Once all of the calcium is stripped form the eriochrome black, the dye changes from reddish-pink to blue.

Salt - Mohr's argentometric titration. Potassium chromate is the yellow-red/brown indicator. Silver nitrate is used to precipitate out silver chloride. Once all of the chloride is removed from the solution, the silver reacts with the chromate to form a reddish-brown silver chromate compound.

Those are there major tests. They can be found in just about any quantitative chemistry or solutions chemistry textbook you might have access to.
Click to expand...

Wow, thanks for the quick response! Exactly what I was looking for. This stuff is amazing and I like knowing the "behind the scenes" if you will. Much appreciated!
 
JoyfulNoise said:
The phenol red reagents are different. For the 2000series comparator block you use the R-0004 phenol red indicator. For the midget comparator you use the R-0014 phenol red. The acid/base demand reagents are different as well.
Click to expand...

Different as in the same phenol red but different concentrations to suit the sample size?

I was recently comparing the Taylor pH test that came with my K-2006 to the BlueDevil (Valterra), both use different sample sizes and whilst the Taylor has a combined phenol red/chlorine neutraliser the BlueDevil uses a <0.1% Sodium Thiosulfate as a separate chlorine neutraliser.
 
AUSpool said:
Different as in the same phenol red but different concentrations to suit the sample size?

I was recently comparing the Taylor pH test that came with my K-2006 to the BlueDevil (Valterra), both use different sample sizes and whilst the Taylor has a combined phenol red/chlorine neutraliser the BlueDevil uses a <0.1% Sodium Thiosulfate as a separate chlorine neutraliser.
Click to expand...

Yes, the concentrations are different. The midget comparator block uses a 4.5mL sample size while the 2000 series block uses a 44mL sample size. So the R-0014 is a lot "thinner" looking (less concentrated) than the R-0004.

Thiosulfate works as a dechlorinator but it is not pH neutral. It tends to raise pH a bit. The Taylor phenol red has a mixture of dechlorinator chemicals in it that remove chlorine in a pH neutral way. The Taylor reagents are far, far better.
 

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^Very interesting Matt, and that includes your original post with regard to the chemistry of all the tests.

CH - I notice undisolved solids or suspention when I do this test. Is this the magnesium hydroxide where the more magnesium in my water the more undisolved solids in the test vial or if I had a lack of Mg I would'nt have these undisolved solids or Mg(OH)2 suspention?

pH - Back to the pH. When I use Taylor reagent (R0004) in a BlueDevil comparator I get the same colour with a slightly darker shade. It looks like it works but the Taylor comparator uses a 44ml sample while the BlueDevil uses 35.5ml, a reduction of 19%. I'm not accounting for drop size but would it be worthwhile to dilute the R-0004 by 19% to get a little closer?

BluDevil pH comparator with BlueDevil reagent.


BlueDevil pH comparator with Taylor reagent.


*Ive added 300ml of acid. :D
 
Correct, the magnesium hydroxide comes out of solution as a precipitate. If you perform the CH test without using the R-0010, you get something closer to a total hardness (TH) number and then you can see how high your Mg level is by subtracting the two. Do you have a lot of Mg in your water?

As for pH, just use one less drop of reagent. Many people do this already with the Taylor comparator. The color is established by the pH value not by how many drops of R-0004 is added. The number of drops determines the intensity of the color you see in the tube. So decreasing by one drop might actually make the color match a little easier. I, personally, don't like using blue sky as the background. I find the color mixing makes it harder to match. I have a pair of very bright white chase lounge chairs and the mesh fabric makes for a great background.
 
Awesome, thanks Matt. - I often use the white render as a background and think that a white background is the best, I always use a piece of white paper under the tests I do inside on the table.

And that is just a bonus that the CH test is a two in one, CH and total hardness where the total hardness part is mostly due to Mg. I must assume that my Mg comes from the tap water, from memory there is quite a stable relationship between total hardness, CH and MgH in the natrual environment, both marine and fresh. I would have thought that total hardness is more important than just CH but I guess calcium is the chemical of choice to bring up either CH or total hardness anyway.
 
AUSpool said:
Awesome, thanks Matt. And that is just a bonus that the CH test is a two in one, CH and total hardness where the total hardness part is mostly due to Mg. I must assume that my Mg comes from the tap water, from memory there is quite a stable relationship between total hardness, CH and MgH in the natrual environment, both marine and fresh. I would have thought that total hardness is more important than just CH but I guess calcium is the chemical of choice to bring up either CH or total hardness anyway.
Click to expand...

Taylor has a better test kit (K-1722) if one was really interested in total hardness (the indicator used is different and a little bit easier to read).

Actually the reason why magnesium is ignored in pool water is because magnesium scale (magnesium carbonate) is incredibly rare to develop. I believe MgCO3 is something like 5 to 8 times more soluble in water than calcium carbonate. So knowing the magnesium hardness is not really super-important.
 
:hammer: Ar yes, sorry that's me just thinking about myself again. With lots of rain I've only every had low calcium and keep it up to prevent the water leaching calcium from the concrete. High calcium is just as important and pool school deals with CH.
 
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