Same water different readings

[loweran]

I bought a FAS/DPD refill for my TF-100 kit. I took chlorine readings with the old bottle of drops and got a reading of 3FC. Took it with the new drops and got a reading of 5FC. Re-ran the tests again with no change. Which one is right?

 

[frogabog]

Go with the new stuff. If new reagents are different, obviously the old stuff is bad.

Which is weird... since there was a recent report about old reagents testing 2-3 times high. I'd think old/bad reagents would test low like you're seeing vs testing very high personally.

 

[Patrick_B]

Go with the new stuff. If new reagents are different, obviously the old stuff is bad.

Which is weird... since there was a recent report about old reagents testing 2-3 times high. I'd think old/bad reagents would test low like you're seeing vs testing very high personally.

I don't know what the answer is, but I would think old reagents would give you a false high since common logic would say they are weaker....therefore taking more drops. Guess it depends on what happens to them as they break down, and this is probably a bad place for common logic to apply. Whatever the answer, I'd go with the new reagent result. Besides...what are you going to be adjusting by from here on anyhow?

I would be curious too though and just happen to have some old and new. I'll be comparing this weekend to see what I get. In the end, two PPM isn't that big a deal if it's a 10 mL test to me.

 

[loweran]

Could the new stuff have been sitting on the shelf for a long time? Maybe one possibility. I might order another bottle and see if they are the same. Or another possibility is that the old bottle has a defective dropper size?

 

[duraleigh]

The R-0871 is light sensitive which is why it's in the opaque bottle. I'm not sure if that's helpful, though, because I don't know what happens after it has been exposed to light.

Virtually none of the chemistry we have sits for more than 30 days and it has a promised shelf life of one year from Taylor. My instinct says go with the newer but I don't think this issue has been reported before so I am not sure of the cause.

 

[loweran]

The R-0871 is light sensitive which is why it's in the opaque bottle. I'm not sure if that's helpful, though, because I don't know what happens after it has been exposed to light.

Well, I store it in a kitchen cabinet under the counter, so light should not be the issue.