10 Year old API Nitrate kit accuracy
I wanted to see if a 10 year old API nitrate kit was still accurate so I made a 20ppm KNO3 solution by mixing 1.631g of KNO3 with 1000ml of pure RO water (TDS reads 1ppm) and then by mixing 1ml of that solution with 49ml of pure RO water. I did not need to make other references so I thought that a 50:1 dilution would make 20ppm using the original 1000ppm solution. Only did one test but it really did read 20ppm as the photos show. The LaMotte kit from 1992 read only 2ppm.
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