Photometric determination of total nitrogen. • Oxidative decomposition in the heating block with subsequent interference compensation and photometric determination with 2,6-dimethylphenol in sulphuric acid / phosphoric acid mixture. • All organic and inorganic nitrogen containing substances are oxidised to nitrate in acidic solution. In acidic solution nitrate ions react with 2,6-dimethylphenol to form 4-nitro-2,6-dimethylphenol, which can be evaluated photometrically. • Type: tube test 0-83 • Range: 0.5 - 22.0 mg/l N • Sufficient for: 20 determinations • Sea water suitability: no