Photometric determination of nitrate. • Photometric determination with sulphanilic acid and 1-naphthylamine after reduction to nitrite. • First nitrate ions are reduced to form nitrite ions. In acidic solution these nitrite ions react with sulphanilic acid and 1-naphthylamine to form a red azo dye. • Type: standard test 1-63 • Range: 10 mm cuvette: 0.1 - 1.1 NO3-N / 0.5 - 5.0 mg/l NO3- ; 50 mm cuvette: 0.02 - 0.45 NO3-N / 0.1 - 2.0 mg/l NO3- • Sufficient for: 440 determinations • Sea water suitability: no