Colorimetry with colour comparison card

• visual and photometric evaluation (with PF-11 / photino)
• environment-friendly, without toxic reagents
• economically priced
• convenient handling
• higher accuracy and sensitivity
• with pictographic instructions
• reagent bottles with clear dosing instructions
• compensation of turbidities and colours
• refill packs available

Oxygen determination according to Winkler: in alkaline solution dissolved oxygen oxidises manganese(II) ions to higher-valent manganese hydroxides. In a strongly acidic medium these form manganese(III) ions which can be determined either titrimetrically or colorimetrically after addition of a colour reagent. Most oxidising and reducing compounds interfere, as for example active chlorine, sulphite, sulphide, higher-valent manganese compounds. Organic compounds interfere, if the potassium permanganate consumption exceeds 60 mg/l. This interference can be circumvented by subsequent addition of ammonium hydrogen carbonate solution. 1 mg/l Fe2+ simulates 0.14 mg/l O2.
(Reaction principle analogous to APHA 4500-O (titr.), ISO 5813 (titr.) & DIN EN 25813-G21)

The solubility of oxygen in water depends on the temperature, the pressure and the other components of the water. The oxygen content of a water at the time of sampling is often quoted as the percentage of the possible saturation.