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Why is potassium chromate the star of water analysis? Explore the chemical reaction behind it!
In the field of water quality analysis, chemical oxygen demand (COD) is an important indicator that can quickly reveal the content of oxidizable organic matter in water. Among them, potassium chromate (K2Cr2O7) has become an indispensable "indispensable" for water quality analysis due to its efficient oxidation performance. Star” chemicals. Not only that, the chemical reaction process of potassium chromate also reveals the mystery of environmental chemistry. Let us explore the chemical reaction behind it!
Chemical oxygen demand (COD) reflects the oxidation potential of organic matter in water, and its testing process is related to the development of environmental protection and water resources management.
The meaning and importance of COD
COD is an important indicator for measuring organic pollutants in water, especially in surface water or wastewater. The COD value is directly linked to the quality of the water. It can not only help evaluate the effectiveness of wastewater treatment, but also show the potential impact of discharges on surrounding water bodies. The measurement principle is based on the fact that almost all organic compounds can be completely oxidized to carbon dioxide under acidic conditions. The amount of oxygen required in this process is the basis for COD measurement.
The role of potassium chromate
As a strong oxidant, potassium chromate shows strong oxidizing ability in acidic environment. A common operation is to create an acidic environment by adding sulfuric acid, so that potassium chromate can effectively react with organic matter in the water sample, eventually producing a large amount of Cr3+. In the detection, we use the amount of Cr3+ generated to indirectly reflect the content of organic matter in the water sample.
The presence of potassium chromate makes COD testing an efficient and reliable choice in modern water quality analysis.
Urgently needed calibration and measurement
To ensure that all organic matter is completely oxidized, an excess of potassium chromate is maintained during the test. When the reaction is completed, the remaining potassium chromate needs to be measured to ensure that the amount of Cr3+ can be accurately calculated. The specific operation usually involves the use of ferrous ammonium sulfate (FAS) for titration, and during the titration process, the redox indicator ferronil is added. When the color of the indicator changes from blue-green to reddish-brown, it indicates that all excess Potassium chromate has been reduced.
Potential interfering substances
When conducting COD testing, some inorganic substances may interfere with the results. Chloride submerged in wastewater is the most common source of interference. Chloride reacts with potassium chromate, meaning additional chemical treatment is required to avoid this interference. Sometimes mercury sulfate is added in advance to remove these interferences to extract more accurate COD values.
Regulations and historical background
With the increasing awareness of environmental protection, many governments have set strict standards for COD in wastewater discharge. For example, in Switzerland, wastewater or industrial water can only be discharged into the environment if the COD reaches between 200 and 1000 mg/L. Historically, potassium chromate gradually replaced the earlier unstable oxidant potassium permanganate, which was questioned due to its uneven oxidation ability. The stability and high efficiency of potassium chromate made it the best choice.
The superior performance of potassium chromate in water quality analysis makes it the cornerstone of environmental protection and an important tool for scientific research.
In today's water quality analysis, potassium chromate not only simplifies the testing process, but also improves the accuracy of the test. This highlights the importance of chemistry in our daily lives. In the future, can we still rely on potassium chromate, or do we need to find safer and more friendly alternatives?
