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Re: Nitrates and testing



> From: "Leslie S Keys" <DAVIDB26 at prodigy_net>
> Subject: Nitrates and testing (question)
> 
> I seem to have a bit of an anomaly as far as my Hach nitrate test kit is
> concerned.  I have been adding KNO3 (in the form on saltpeter) at the rate
> of  tsp. for the last 2 days.  I calculated that the concentration - if the
> plants used none - should be at about 6ppm.  However, after the first
> addition the Hach test kit shows concentration as .25 Nitrate nitrogen = 1.1
> PPM Nitrate.
> After the second dose the test showed .35 = 1.5 PPM Nitrate in other words I
> appear to be missing 4.5 PPM NO3.  Previously to the KNO3 addition the kit
> read zero nitrates.

	Did you calibrate the test kit with a solution of known concentration?
It's one of the first things I do with a new kit.

> The test kit is not accurate (or could be I am not performing the test
> properly)

	You are looking at quite low concentrations - is it really possible
to distinguish the colours well enough to get that accuracy?

> The calculations are incorrect - I will put my assumptions later

	See below.

> The plants are eating most of the NO3 / the green water algae have eaten
> most of the NO3

	It can disappear pretty quickly.

> The fluorite substrate has somehow sequestered the NO3 (wild speculation).

	Nitrate is pretty difficult to sequester.

> Saltpeter is not just KNO3

	It should be.

> 75 gallon

288 litres, say 250 L of water.

2.4g of KNO3 at 61% is about 1.46 g of NO3, so about 6 ppm, O.K..

-- 
Paul Sears        Ottawa, Canada