Thermal decomposition of stored bleach

[CarlD]

Our water district uses CC instead of FC so you might want to check that as it will throw off the measurement. According to my brother in-law who works at the regional water district, quite a few plants do this. So you might want to use distilled water instead of tap water or pre-shock the tap water and let the chlorine drop a bit before the test.

I'm not sure I understand this--if you are testing your LC/bleach for its strength, you want to test FC. I'd be shocked if CC > 0 shows up.

CC is a perfectly reasonable test of tap water to see if there's some contamination of that resulted in a CC > 0.

[mas985]

My point was to make sure that there is no CC in the tap water or the results may not be very accurate.

Chemgeek had mentioned that one should measure the FC of the tap water before adding the LC which is a good idea but many water districts use CC instead of FC in tap water, it lasts longer. This could cause a significant error in the LC measurements if not taken into account. Adding FC to tap water with CC will convert some of the CC into FC but from what I understand about the process, there is a net loss of FC.

So if you use tap water with CC and then add LC, it is likely to underestimate the strength of the LC. I am sure that Chemgeek has a way to take the CC conversion into account but it may just be easier to avoid it all together buy using distilled water or water without any CC.