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Re: NO3 and PO4 in Takashi Amano Aquaria -- COD

John Fitch wrote:

  As for chemical oxygen demand, how does one
measure that?  Just curious.

What tests I've seen are colorimetric and require a spectrophotometer. They're typically marketed to wastewater management. As for method, all I remember is potassium dichromate digestion, and there was another that used mercury salts for instances when chloride was high. The "kits" usually have the reagents pre-measured in crystal vials to minimize exposure to the chemicals -- you just add the sample to the vial, and stick it in the spectrophotometer. I think I remember that heating is involved, too, though that may only be when a particular method is used. Hanna Instruments has a meter etc., and Chemetrics has a prepared test that runs in the Hach spectrophotometers, but those are the only specific companies I recall. I'd say this would be an expensive test to run.
Chuck Huffine
Knoxville, Tennessee