Any real difference between Taylor's R-0871 and R-0872?

[hotubbie]

Taylor has both an R-0871 and R-0872 FAS-DPD Titrating agent that they sell separately under the guidance that you will need the R-0871 to measure chlorine and the R-0872 to measure bromine. The instructions seem very similar and in previous DPD test kits, you could use the same reagents and then apply the 2.25 multiplier for the bromine ppm levels.

Is there really something different between R-0871 and R-0872 or is it simply a label to sell one product as two?

 

[ajw22]

@Richard320 @JoyfulNoise ideas?

 

[Richard320]

Not a clue.

 

[JoyfulNoise]

Same chemical - ferrous ammonium sulfate (FAS), but slightly different concentrations so that the number of drops and multiplier are easier to figure out. If you use the R-0872 to titrate chlorinated water with, then you’ll need to adjust the multiplier or else you’ll get the wrong value for FC and CC.

 

[hotubbie]

@JoyfulNoise , so if the concentration is different and the equivalent ppm for bromine is more than chlorine does that mean the R-0872 (bromine) is less concentrated than the R-0871 (chlorine)? Since they are both about the same price perhaps it is best to use the R-0871 and just do the multiplier (which I don't mind). Is that correct, or is the reverse direction where the R-0871 is the less concentrated of the two?

Thanks for the help!

 

[JoyfulNoise]

@JoyfulNoise , so if the concentration is different and the equivalent ppm for bromine is more than chlorine does that mean the R-0872 (bromine) is less concentrated than the R-0871 (chlorine)? Since they are both about the same price perhaps it is best to use the R-0871 and just do the multiplier (which I don't mind). Is that correct, or is the reverse direction where the R-0871 is the less concentrated of the two?

Thanks for the help!

You have to take into account the molar mass difference between bromine and chlorine so you can calculate the molarities involved. When you do that, the concentration of FAS in the R-0872 is slightly higher than in the R-0871.

I honestly don't know why Taylor goes to such lengths to provide two, slightly different, versions of the same reagent. Given that everyone has access to a calculator or a phone with a calculator on it, it seems a bit strange to me to offer both reagents. I would just use whatever you find the most convenient and easy to get. Most every test kit I see has R-0871 in it and so I would just use that. But if you're the only one doing the testing and dosing, it's up to you.....

 

[ewanwh]

From what I've figured out, switching between the two reagents will give you a 10% variance in test results as long as you are using the same instructions.

The K-2006 instructions for R-0871 with chlorine is: 1 drop = 0.2 ppm in 25mL sample, 1 drop = 0.5 ppm in 10mL sample.

The K-2106 instructions for R-0872 with bromine is: 1 drop = 0.5 ppm in 25mL sample, 1 drop = 1.25 ppm in 10mL sample.

Therefore, if you are using R-0871 with bromine, you need to use the chlorine instructions (not bromine) and then multiply the result by 2.25. From the instructions above it's clear that the two reagents are actually very close in concentration. With R-0871 you would multiply 0.2 ppm (chlorine) x 2.25 = 0.45 ppm per drop for bromine. Compare that to 0.5 ppm (bromine) per drop with R-0872. This is a difference of 10% in the results.

For my home hot tub purposes this makes R-0871 and R-0872 interchangeable.