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What are the interference effects when the residual chlorine meter is measured?

by:BOQU     2023-04-06
What are the interference effects of the residual chlorine meter? The residual chlorine meter is equipped with a large LCD display, which makes the measured display value easier to read. Using DC power supply, it is safer to use. The power line is also a 4-20mA output signal current-carrying line, which makes the connection easier. The 4-20mA output signal can be transmitted to a recorder or other devices that can receive 4-20mA signal, such as PLC, DCS and personal computer. The transmitter has manual and automatic temperature compensation function, and the temperature compensation adopts pt100 temperature electrode. The terminal board can be pulled out to make field wiring more convenient and quick. Residual chlorine refers to the chlorine remaining in the water after the water has been in contact with chlorine-based disinfectants for a certain period of time. There are three forms of residual chlorine: 1. Total residual chlorine: including free residual chlorine and combined residual chlorine. 2. Free residual chlorine: including HOCl and OCl-, etc. 3. Compound residual chlorine: including NH2Cl, NHCl2, NCl3 and other chloramine compounds. The role of residual chlorine is to ensure continuous sterilization and prevent water from being re-polluted. However, if the amount of residual chlorine exceeds the standard, it may aggravate the odor produced by phenols and other organic substances in the water, and may also generate CHCl3 and other organic chlorinated substances with 'three causes' effects. Determining the content and state of residual chlorine in water is extremely important for doing a good job in drinking water disinfection and ensuring the safety of water hygiene. There are many methods for measuring residual chlorine. When compound ions are formed, the free available chlorine reacts with the DPD reagent immediately to produce red color, and the addition of iodide ions acts as a catalyst to make the combined chlorine also react with the reagent to develop color. Measure the absorbance respectively to obtain free chlorine and total chlorine, and subtract free chlorine from total chlorine to obtain combined chlorine. The influence of interference on the residual chlorine meter: 1. The presence of greater than 250mg/l alkalinity or 150mg/l acidity in water such as CaCO3 etc. will inhibit all color development or the color will fade immediately. Neutralize the sample solution to pH 6-7 with 1N H2SO4 or 1N NaOH. 2. Monochloramine will gradually increase the free chlorine reading. Read within one minute, each 3.0mg/l of monochloramine will increase the free chlorine reading by 0.1mg/l. 3. Bromine, iodine, ozone and oxides of manganese and chromium will increase the free chlorine reading. 4. To reduce the influence of Mn4+ and Cr6+, adjust the pH to 6-7 as above. Take 25ml water sample, add 3 drops of 30g/l KI solution, mix and wait for one minute. Add 3 drops of 5g/l Na2AsO3 and mix (according to the 'Water and Wastewater Standard Test Method', 0.25% thioacetamide solution can be used instead of NaAsO2, and 0.5ml 0.25% thioacetamide is added to each 100ml water sample). If chromium is present, it reacts with DPD in both assays, readout. This reading is then subtracted from the chlorine reading obtained from the initial analysis. Related Products
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