What is the difference between chloride, chloride and residual chlorine and how to use chloride test paper?

- Jul 07, 2020-

What is the difference between chloride, chloride and residual chlorine and how to use chloride test paper?

What is the difference between chloride and chloride?

Chloride is an ionized Cl-. It measures the concentration of chloride ions dissolved in water. Chloride refers to the low-Cl and belongs to the atomic state. But chloride, which is often used in water treatment, generally refers to ionized chloride.

What is residual chlorine?

Residual chlorine refers to the oxidizability produced by the water body after being exposed to the oxidizing bactericide for a certain period of time, which is expressed by Cl (atom), which represents the oxidizability of the water body. When chlorine or hypochlorous acid is added to water, it will firstly hydrolyze and dissociate, mainly decomposing into HCLO, CLO- and other substances. Since HCLO is an electrically neutral molecule with a small molecular weight, it easily penetrates the surface of negatively charged bacteria and It penetrates into the cell through the cell wall, and destroys the enzyme system of the bacteria through oxidation to kill the bacteria.

The production of tap water in my country is produced and inspected in accordance with the national sanitary drinking water standards. It is the general index of hypochlorite, monochloramine, dichloramine, trichloramine, and very few chlorides (chloride ions), etc., as the important indicators of factory water. In "National Sanitary Standards for Drinking Water" GB5749-2006, chloride is <250mg/L. The residual chlorine in the water plant is 0.3-4mg/L (chlorinated disinfection). The residual chlorine in the end of the pipe network is ≥0.05mg/L. This requirement is not specified in the chloride standard. Chloride refers to all chlorine-bearing substances. Chloride ion covers chloride-bearing substances as well as many other substances.


The most original method for determining the content of chloride, the liquid titrated with silver nitrate and potassium chromate indicator is calculated based on the titration amount when the liquid is just reddish, and the calculation formula is chloride = (35.5×nitrate The concentration of silver acid (ml) × silver nitrate concentration (mol/L) × 1000]/volume of measured liquid (ml) is used to calculate the concentration.


① The color change is not very obvious.

② It is greatly affected by the color. It is difficult to distinguish whether the color has reached the end point during the titration.

Chloride test paper: 500-1000-1500-2000-3000mg/L 100 times/box.

Chloride test paper


① Simple operation-very simple operation steps, no other auxiliary consumables are needed.

②Accurate and reliable-classical colorimetric analysis, multi-level test requirements, visual reading with colorimetric card.

③ Convenient and fast-it only takes 0-1 minutes to test the samples, and it is convenient to carry out for outdoor testing.

④ Stable and reliable-Packed in dry and sealed drums, the shelf life is up to 1-3 years.


① Draw the test strip into the liquid to be measured for 1 second and take it out

② Remove the excess solution from the test paper

③ ③Compare with color card in 2 minutes reaction


① Do not touch the reaction end of the chloride test paper when removing the chloride test paper to avoid contaminating the chloride test paper and affecting the test results.

②After taking out the required amount of chloride test paper, seal the remaining chlorine test paper in a sealed state to avoid high temperature or direct vision.

③ The PH value of the liquid to be tested should be between 5-9. Decolorization treatment is required before the liquid that seems colorless or light color, and the color is too dark.

④ Before using, please carefully read the operating instructions and precautions on the barrel.