Photometric determination of the COD without use of mercury salts. • Photometric determination of decrease in chromate concentration after two hours and oxidation with potassium dichromate/sulphuric acid/silver sulphate at 148 °C without use of toxic mercury salts • Chloride contents below 2000 mg/l are eliminated by a simple filtration pretreatment step using a special cartridge and do not interfere. • The chemical oxygen demand of a water is determined by silver-catalysed oxidation with potassium dichromate/sulphuric acid at 148 °C during a two hour period. • Type: tube test 0-26 • Range: 15 - 160 mg/l O2 • Sufficient for: 20 determinations • Sea water suitability: no