Issues with the preparation of COD standard solutions
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Why is sulfuric acid added when preparing COD standard solutions using potassium hydrogen phthalate, and is there a specified amount for its addition?
The pH value of potassium hydrogen phthalate is suitable for the growth of microorganisms in water; adding a small amount of strong acid can make the solution more acidic, thereby creating conditions unsuitable for microbial growth.
This post was last edited by sunshineda_VGMP on 2019-5-31 at 17:27. The purpose of adding 5 mL of sulfuric acid as specified in the standards for detecting organic matter in wastewater using the potassium dichromate method is to ensure that the water sample and the standard solution react under acidic conditions. The specific method for preparing the 2.0824 mol/L potassium hydrogen phthalate standard solution is as follows: Weigh 0.8502 g of potassium hydrogen phthalate that has been dried at 105°C for 2 hours, dissolve it in water, and dilute the mixture to 1000 ml. After mixing well, the COD standard solution is obtained.