testing for bromine- is it chlorine or bromine?!

[archer636]

I primed the spa with sodium bromide, added chlorine as oxidizer (2-step method outlined in the sticky post). I am using Taylor K-1000 to test for bromine. Question is, is it chlorine or bromine I am looking at?! they both use the same reagent (OTO) so I have no clue if I am measuring the oxidizing bleach that I added, or the sodium bromide turned into bromine? Do I need to wait a certain amount of time for the chlorine to do it's magic before measuring bromine levels?

Also, I understand it is recommended to use Taylor K-2106 for bromine. Is it another color-matching kit? or will I be counting drops? there is surprisingly little information available on this kit, I would like to know how it works before spending $57.

 

[pooldv]

I am not very familiar with bromine but this should help until somebody comes along.

How do I use Bromine in my spa (or pool)?

 

[wayner]

I have been told that you can just use the test chemicals for chlorine and multiply by 2.25 for bromine. So when using the FAS-DPD chlorine test kit to test for bromine for a 25ml sample the FC reading is drops*.2*2.25 or drops *.45. So just using drops*.5 is close enough. This makes it easier for me to use one kit to test my SWCG chlorine pool and bromine spa.

 

[JoyfulNoise]

You can't differentiate chlorine from bromine. The test should really be called a "total halogen" or "free halogen" test because chlorine, bromine and iodine will all make the dyes change color.

In your spa, you just have to assume that the dominant halogen is bromine because chlorine will immediately react with the bromide to form bromine and it (chlorine) will be used up very quickly.

Incidentally, this is why you should NEVER add bromine to a swimming pool. It creates a constant chlorine demand which cannot be accurately tested for.

 

[archer636]

You can't differentiate chlorine from bromine. The test should really be called a "total halogen" or "free halogen" test because chlorine, bromine and iodine will all make the dyes change color.

does this apply to FAS-DPD test also? e.g both chlorine and bromine will make it turn pink?

 

[JoyfulNoise]

does this apply to FAS-DPD test also? e.g both chlorine and bromine will make it turn pink?

Yes.

 

[archer636]

Yes.

then how come K-2106 is indicated for bromine testing and not chlorine? or is that just a marketing gimmick?

 

[JoyfulNoise]

Marketing gimmick. The K-2106 has the FAS-DPD titration test for halogens, pH, TA and CH tests. That's all that matters in a bromine spa because one does not use cyanuric acid in a bromine spa.

In general chemistry terms, the DPD indicator dye turns pink in the presence of any halogen (chlorine, bromine and iodine). It does not distinguish between halogens.