With the development of the industry and the discharge of a large amount of industrial wastewater, the water pollution situation in our country has become increasingly serious. The measurement of the permanganate index value has become a key factor in water source detection. It is one of the key assessment criteria for evaluating the level of organic and inorganic pollutants in water quality.

What are the situations that need to be paid attention to in the measurement of the permanganate index value?

The permanganate index value is expressed in mg/L of oxygen, which is the amount of potassium permanganate solution consumed during the treatment of water quality samples under certain standards, using potassium permanganate solution as the reducing agent. The main source of error in the determination of the permanganate index value using the acidity or alkalinity determination method is the asymmetry of the potassium permanganate solution, the acidity of the reaction management system, the heating time, and the bias introduced by poor measurement.

Therefore, to eliminate bias and obtain a relatively accurate data, it is necessary to handle the following several issues during the measurement of the permanganate index value:

1. Prepare a relatively stable potassium permanganate solution solution: The concentration of the potassium permanganate standard solution has a significant impact on the calculation of the blank value and the true value of the sample, and should be adjusted as close as possible to 0.0100 mol/L. The concentration of potassium permanganate will affect the final measurement results.

2. Maintenance of acidity in the reaction management system: The titration method using potassium permanganate solution with a high acidity or alkalinity for the measurement of the permanganate index value belongs to the oxidation-reduction reaction reaction. The acidity of the reaction management system has a significant impact on the rate and direction of the entire reaction. Therefore, the acidity must be suitable, otherwise it may cause errors in the measurement results. To ensure that the reaction can proceed reasonably, the titration method using potassium permanganate solution with a high acidity or alkalinity requires the acidity of the water quality samples to be between 0.5-1.0 mol/L, and it is forbidden to use hydrochloric acid or sodium cyanide.

3. Influence of heating time on measurement results: Under the standard conditions of a certain temperature and reaction rate for chemical changes, the duration of the reaction speed will affect the level of the reaction. The air oxidation method using potassium permanganate solution with a high acidity or alkalinity to determine the permanganate index value only measures the amount of oxidizing substances in the water quality samples that are oxidized by the potassium permanganate solution within the required time, and does not represent the total amount of oxidizing substances that can be oxidized in the water quality samples. The reaction speed will immediately affect the final measurement results.

4. Strict control of measurement standards: The permanganate index value is a relative conditional indicator value, which is the measurement result under certain standards. Its measurement result is related to the acidity value of the water solution, the concentration of permanganate, the temperature and time of heating. Therefore, it is necessary to strictly implement the actual operation requirements during the measurement to ensure comparability of the results.