"Greg G." wrote in message
...
Also, to insure that the information I am tendering is accurate, I
remixed the standard solution and re-tested with each kit.

The Hagen kit contains a reagent #3 that is apparently comprised of
zinc dust mixed with N-1 Naphthylethylene-diamine Di HCl. Each time
the test is run, a different result is obtained. Apparently, the zinc
does not stay in suspension correctly, no matter how much the reagent
bottle is shaken. It masses together to the point that it makes
dispensing the solution near impossible - for it clogs the tip. This
kit is one month old.

I've had the same experience with reagent 3 in the Hagen NO3 kit. It would
clog up the bottle tip so the liquid barely came out. I even contacted Hagen
about it, and they sent me a replacement reagent 3, but it had the same
problem. Apparently, you have to shake it for a couple of minutes before
this zinc mass dislodges from the bottom of the bottle. Hagen should
definitely address this. I finally bought a Seachem NO2-NO3 test kit and
that one works fairly well.

The Tetra kit simply says NO3- on it. I have long ago lost the
enclosed pamphlet so I am uncertain which method it uses. The minus
symbol implies to me that the reading is nitrate-nitrogen.

Considering the Tetra test kit scale, I doubt it measures NO3-N. (Few test
kits do.) The minus sign simply indicates the negative charge of the anion.

I suppose that I could mix up various mixtures and use that to
calibrate/create my own scales for use with the kit until it is
expended... but is it worth the trouble?!

You could always dose without testing, as I often do. For quite some time,
according to my test results, I have had to add the same amount of KNO3 each
time I dose. So now I don't test much, I just add this same amount twice a
week.
__
Alex
pcalex (at) hotpop.com