What is the measurement principle of the residual chlorine meter?

Residual chlorine analyzer is a commonly used analytical instrument, which can measure residual chlorine, pH value and temperature at the same time, and can be widely used in continuous monitoring of residual chlorine and the pH value of various water qualities in electricity. electricity, aqueducts, hospitals and other industries .

Measuring principle of residual chlorine meter

When the water sample does not contain iodide ions, free available chlorine reacts immediately with DPD reagent to produce a red color. The addition of iodide ions will act as a catalyst, causing the combined chlorine to react with the reagent to develop color.

Measure absorbance to get free chlorine and total chlorine respectively, and subtract free chlorine from total chlorine to get combined chlorine.

The impact of interference on the residual chlorine meter

1. The presence of alkalinity above 250mg/l or acidity of 150mg/l in water such as CaCO3 etc. will prevent any 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 in one minute, each 3.0 mg/L of monochloramine will increase the free chlorine reading by 0.1 mg/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 a 25ml water sample, add 3 drops of 30g/L KI solution, mix and wait one minute.

Add 3 drops of 5g/lNa2AsO3 and mix (according to the \"Standard Test Method for Water and Wastewater\", a 0.25% solution of thioacetamide can Andre used instead of NaAsO2 and 0.5 ml of 0.25% sulfur is added to each 100 ml of acetamide of water sample).

If chromium is present, it reacts with DPD in both assays, reading.

Subtract this reading from the chlorine reading of the original analysis.

Tag: Chlorine Meter