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Hach CO2 test kit

Scott H.,

I also use the Hach CO2 test kit(Cat.No.1436-01). I got this after trying
to understand why the CO2/KH/pH table wasn't working for me. Recent posts
have enlightened me on some reasons or possibilities as to why this may be.
As far as the test kit goes, it seems that the Low Range test(increments of
1.25 mg/l) does produce very faint color changes that are hard to
distinguish while the High Range test(increments of 5 mg/l) produces an
abrupt and clearly identifiable color change. Most of the time I use the
Mid Range test(increments of 2 mg/l). This provides a color change more
noticeable than the Low Range test and limits the error to 2 mg/l. To
standardize the tests even more, I keep a white piece of paper in the test
kit box that I set the test vial on when I am looking for the color change.
I also try to use the same light source which is easy because I run all the
tests at the same kitchen counter under the same light. The test kit is a
field unit and I have tried to run CO2 tests in the field but, because of
the variability of outdoor light, the Low Range test is especially hard to
read. I have not yet spoken with Hach about this. 

--- Eric