Testing bromine?

[ethany]

I have a Taylor K-2006 test kit. I just filled my hot tub a few days ago, can I test for Bromine like I would chlorine? Use dpd powder and reagents? I realize it would be easier to just use chlorine but I would really like to use up the bromine(sodium dichloro-s-triazinetrione 82.5% sodium bromide 14.7%).

How often do I need to test the water? I use it a few times a week and my wife even less.

 

[chem geek]

[EDIT] Corrected ppm total bromine per drop for sample sizes; I had it reversed in my first draft of this post. [END-EDIT]

You can use the FAS-DPD chlorine test and just realize that when you are testing Free Chlorine (FC) in that test that you are really testing Total Bromine if you multiply your result by 2.25. So if you use a 25 ml sample, then every drop of titrant represents 0.45 ppm total bromine while if you use a 10 ml sample then every drop of titrant represents 1.125 ppm total bromine. You don't bother with the R-0003 for the CC test since it won't measure anything relevant -- the FC test measures both bromine and bromamine together (unlike chloramine that doesn't register in the FC test, but does in the CC test).

 

[Melt In The Sun]

Richard, very concise and informative answer...but you switched the sample sizes! Each drop of titrant in a 10 mL sample represents 1.125 ppm bromine, and each drop in a 25 mL sample is 0.45 ppm

.....right?

 

[dmanb2b]

If I'm not mistaken, I believe you can purchase r-0872 reagent as well to test for Bromine? Not sure if that makes the sample/drop counting process more simple.

 

[chem geek]

Richard, very concise and informative answer...but you switched the sample sizes! Each drop of titrant in a 10 mL sample represents 1.125 ppm bromine, and each drop in a 25 mL sample is 0.45 ppm

.....right?

Yes, I got it backwards and I've edited my post. Thanks for catching that.

If I'm not mistaken, I believe you can purchase r-0872 reagent as well to test for Bromine? Not sure if that makes the sample/drop counting process more simple.

Yes, you are correct and they do slightly adjust the concentration in the reagent so that one drop is 0.5 ppm with a 25 ml sample and 1.25 ppm for a 10 ml sample.

 

[ethany]

Thank you for your reply,good to know. Two more questions,which is a easier and safe sanitizer Chlorine or bromine? Also can you put salt in your hot tub like you do a pool?

 

[chem geek]

Some people prefer one over the other. Technically, chlorine is safer in the sense that the disinfection by-products it produces are generally less harmful than those formed from bromine (in particular the trihalomethanes). However, bromine is seen by some to be more convenient since you can have a floating bromine tab feeder maintaining bromine levels if you don't use the tub regularly. With chlorine, you'll have to add chlorine every day or two even if you don't use the tub. If you use it regularly (almost every day), then it's not a big deal to just add chlorine when you get out of the tub. See the following links for more info on how to use bromine and chlorine:

Using Bromine in a Spa
Using Chlorine in a Spa

 

[PaulR]

You don't bother with the R-0003 for the CC test since it won't measure anything relevant -- the FC test measures both bromine and bromamine together (unlike chloramine that doesn't register in the FC test, but does in the CC test).

This is a change from what you wrote here in March, "add the R-0003 reagent before you add the FAS-DPD titrating drops." Please confirm one way or the other... thanks! (I've been cruising for bromine info lately or I probably wouldn't have noticed this difference.)
--paulr

 

[chem geek]

I was wrong before when I thought that you needed the R-0003 to measure bromamine. It turns out that bromamine is a strong enough oxidizer to react with the dye in the FC test. The chemistry behind this (as described in this link) is thought to be that at pool pH monobromamine (NH₂Br) readily forms a more active monobromammonium ion (NH₃Br⁺) whereas monochloramine (NH₂Cl) does not. At pH 7.5, about 10% is in the form of this monobromammonium ion. This ion is more reactive, possibly by more readily converting to ammonia and positively charged bromine atom (Br⁺) when reacting with other organic chemicals. I've now edited that older post. Thanks for catching that.