In article , eetmail-
says...

This brings up a question I have. I lost the little measuring scoop for
the powdered reagent that came with my Seachem nitrate test kit. Before
I lost the scoop, I always noticed that the scoop of powder didn't quite
dissolve (the solution was saturated). The kit came with a 10 ppm
standard so I tried testing without the measuring scoop by putting the
powder in to saturation. I got the expected colors for RO water, a tank
that's been stable around 2-3 ppm nitrate, and the 10 ppm nitrate
standard. I don't have enough standard solution to run every time. Am
I OK assuming that as long as the powdered reagent is slightly in excess
the kit will give a reasonable answer?


In my experience the powdered metal is always in excess. Your Seachem test kit is
very likely using a similar assay. My bet is that it should work just fine so long
as you ensure sufficient reagent to reach saturation. Perhaps a lurking analytical
chemist can jump in at this point and say something more definitive.

Now that we are talking nitrate test kits, I looked again at the Hagen kit. It
uses a variation on the theme, cadmium instead of zinc. Kordon has two nitrate
tests that both use cadmium. (They also have an informative web site with detailed
product information for the technically inclined reader: http://www.novalek.com/)
I thought cadmium was on the list of things to avoid and am surprised to see
elemental cadmium in a consumer test kit. I suppose this is nothing to compare
with the amount of cadmium in a NiCd cell, but it makes me think twice about
running tests on the kitchen countertop. A while back I think I saw some kit that
used pyridine. Maybe time to shun the test kits and embrace Tom Barr's EI !