Heating a mixture of water sample, potassium dichromate digestion solution, silver sulfate solution (silver sulfate as a catalyst can effectively oxidize linear fatty compounds), and concentrated sulfuric acid to 170 ℃ will cause a color change after the oxidation of organic matter in the solution by dichromate ions. The analyzer detects this color change and converts it into BOD value output. The amount of dichromate ions consumed is equivalent to the amount of oxidizable organic matter.

The reducing inorganic substances in water samples, such as nitrite, sulfide, and ferrous ions, will react with potassium dichromate, affecting the measurement results. The amount of potassium dichromate consumed by them will be recorded in the measurement results, making the measurement results higher. The interference of chloride ions in water samples can be eliminated by adding mercuric sulfate, as chloride ions can form very stable mercuric chloride with mercury ions.

1. Select valve components: Choose reagent sampling timing, flexible and diverse channels, versatile functions, easy maintenance, high lifespan, and other advantages.

2. Micro metering component: achieves precise measurement of reagents through a visual photoelectric system, overcoming quantitative errors caused by wear of peristaltic pump tubes; At the same time, precise quantification of trace reagents has been achieved, with each dose being only 1 milliliter, greatly reducing the amount of reagents used.

3. Sample injection component: peristaltic pump negative pressure suction, there is always an air buffer zone between the reagent and the pump tube to avoid corrosion of the pump tube; At the same time, it makes the mixing of reagents more concise and flexible.

4. Sealed digestion component: High temperature and high pressure digestion system accelerates the reaction process and overcomes the corrosion of equipment caused by the volatilization of corrosive gases in open systems.

5. Reagent tube: Imported modified PTFE transparent hose with a diameter greater than 1.5mm is used to reduce the probability of particle blockage in water samples.