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Water quality testing-how do you detect residual chlorine in water?

What is the residual chlorine?

Chlorine, commonly known as bleaching powder, is the general term of free chlorine and binding chlorine in water after contact with the water after contact with the water after a certain time contact. After the chlorine is put into the water, the chlorine amount is left out in addition to a part of chlorine in the water, such as bacteria, microorganism, organic matter and inorganic matter in the water, and the chlorine amount is called the chlorine.

Where does the residual chlorine from the drinking water come from?

The residual chlorine in the tap water is the remaining amount after adding chlorine disinfectant to the water before the water works. The water plant should not only guarantee the effluent of the water plant, but also guarantee the amount of residual chlorine when the tap water reaches the end of the pipe network. The purpose of adding disinfectant in water is to kill the tap water. Microorganisms in the water supply network, including algae and pathogens in water, can prevent the spread and epidemic of water borne infectious diseases.

Why do we have to detect the residual chlorine?

At present, the purifying mode of tap water in our country is chlorine gas sterilization.

Chlorine gas has serious harm to the human body. It stimulates the eye, nose, throat and upper respiratory tract. It causes acute pulmonary edema and pneumonia. When the concentration is high, the respiratory center can be paralyzed and "flash death" is paralyzed. Chronic inhalation of low concentration chlorine will cause chronic poisoning, causing a large number of free radicals and accelerating the aging of the body. The main disease is nose. Inflammation, chronic bronchitis, emphysema, cirrhosis, atherosclerosis, and even cancer.

Long term drinking water containing excess chlorine in pregnant women can affect the growth of the heart and lungs of the fetus, which may lead to arrhythmia, heart failure, and pulmonary functional disorders in the newborn.

Long-term use of water containing residual chlorine in the bath, chlorine will cause hair to produce dry fracture bifurcation, and also make the skin bleach, skin layer and produce allergies. When chlorine and organic substances such as sweat interact, it is easy to cause three nitrogen chloride in the surrounding air, easy to damage the eyes and throat. Chlorine will damage the breath after breathing through the respiratory tract through the respiratory tract. Cells are easy to cause asthma and emphysema.

The pool pool has more residual chlorine: it is harmful to the respiratory system. It is easy to react with organic matter in the water and produce chloroform and other carcinogens. It can cause damage to the skin cells and cell interstitium, and easily cause skin dry, chapped, papules, acne, aging, or palm.

Quantitative detection of residual chlorine

Residual chlorine analyzer

The residual chlorine analyzer (LH-C01/LH-C10) is mainly used in the detection of chlorine containing disinfectant residues in water (the concentration of chlorine in the book), using the DPD photometric method. The results are in accordance with the national standard. It is the advantage of the instrument to replace the national standard method.

LH-C01/LH-C10 operation specific steps


When the reagent is dissolved, it needs to be completed within 5 minutes. The determination will affect the accuracy after 5 minutes. A small amount of reagent will not affect the detection.

Any liquid or foreign matter entering the coloring tank may damage the instrument. The coloring tank should be cleaned and placed in the colorimetric bottle.

When the concentration of residual chlorine in the sample is high, the deep red color of the reagent is quickly faded. This is because the reagent which is oxidized and coloured is bleached by the residual chlorine. If the water sample concentration exceeds the instrument range, the water sample is diluted with distilled water or pure water (after firing to cool) and then remeasured, and the measured multiplication like dilution multiple is the water sample concentration value.

The reagent bag belongs to the easy tear bag, and any surface can be torn open.

After each test, we need to clean the color bottle many times after cleaning this color bottle. If the inner wall is dirty, the alcohol -10% hydrochloric acid can be washed with (1+1); then the water is washed thoroughly with water.

There are no water stains, scratches, dust and fingerprints on the cuvette surface.

More attention should be paid to the process of residual chlorine detection -


Contact: Mike Zhang

Phone: +86 13732228065

Tel: 0574-55123801

Email: mikezhang@sinotester.com

Add: 3/F Jiaofu Building , Middle No.928 Songjiang Road Yinzhou Dis. Ningbo City, Zhejiang, China

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