# Re: mistake ref solution

• To: <Aquatic-Plants at actwin_com>
• Subject: Re: mistake ref solution
• From: Thomas Barr <tcbiii at earthlink_net>
• Date: Tue, 14 May 2002 11:56:59 -0700
• In-reply-to: <200205140748.g4E7m2623280 at acme_actwin.com>
• User-agent: Microsoft-Outlook-Express-Macintosh-Edition/5.02.2022

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> A level 1/4 tsp = 1.67 grams on average(Cooke's/Grant's brands => based on
> 20 samples and 3 different runs with 3 different teaspoons on an analytical
> microscale). You can add this to a 1 liter pure H2O. This will give you
> .61325 grams of NO3 in that water (and .387 grams of K+). Since ppm =
> mg/liter you'll now have 613.25ppm (or no# of milligrams in one liter) NO3
> in this sample. Take 10mls of this solution and add it to another 1 liter of
> pure H20. 10mls/1000ml in a liter = 6.1325ppm of NO3 in this reference
> sample. Gauge your test kit against this. The ref solution is pretty
> accurate(+,- 0.2ppm) even if you are a little off(weights/volume, different
> 1/4 teaspoons, ml doses are a little off, KNO3 not 100% pure etc). Try to be
> accurate though. This should get a better idea of what's happening with all
> the kits that are out there and their accuracy within the range plant folks
> need for NO3 measurements.

Not thinking (again).

I left the ratio(for a 1 gram sample) and forgot to multiply by the 1.67
grams in a 1/4 teaspoon. So it should read 1.020 grams of KNO3 and 0.646
grams of K+ PER 1/4 TEASPOON.

With the dilution that will give 10.2ppm of NO3 and K+ of 6.46 ppm in this
reference sample.

Thanks for pointing it out Ken.

Regards,
Tom Barr

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