Re: Aquatic Plants Digest V2 #485

Paul wrote:
<<The nitrate tests I have seen use a two-part reaction in which
the nitrate in the original sample is first reduced and then measured
in another form.  Putting nitrate into the mixture at the end of the
test - after the second step - may well not work.>>

The cadmium reducing agent is still around and active after the diazotiztion
coupling reagent is added that produces the pink color.  I have found that a
drop or two of nitrate solution will always turn the test solution dark pink
even after both reagents are dissolved, unless something is wrong.  In the
particularly problematic test kit (wardley), I noticed that if the diazo
tablets (tablet #2) were slightly colored or appeared hydrated, the test
would give a false 0 ppm result when in fact the NO3 was around 10 ppm.

Bill Cwirla