Photometric determination of Ammonium. • Photometric determination as indophenol • At a pH value of about 12.6 ammonium reacts with hypochlorite and salicylate. in the presence of sodium nitroprussiate as catalyst to form a blue indophenol. • Type: tube test 0-03 • Range: 0.04 – 2.30 mg/l NH4-N; 0.05 - 3.00 mg/l NH4+ • Sufficient for: 20 determinations • Sea water suitability: yes, after dilution (1:2)