I have some questions regarding the extraction of humic acid from coal
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Dear colleagues: Hello everyone. I have been working on the extraction of humic acid from coal recently. In accordance with the GB/T11597-2001 standard, we use a volumetric method – sodium pyrophosphate solution is used to extract total humic acid, while sodium hydroxide is used to extract free humic acid. So, is the humic acid referred to in common usage the sum of total humic acid and free humic acid? So, is the humic acid referred to in the industry the total humic acid? This is a bit confusing ； During the process, the results varied quite a bit several times; could it be due to incomplete extraction? I would appreciate advice from experienced colleagues. Thank you!
Humic acid can be expressed as total humic acid and free humic acid, depending on the basis used for company settlements. We are currently settling based on free humic acid, so we focus on the content of free humic acid. The main thing is to ensure the blanks are accurate; ammonium ferrous sulfate must be recalibrated each time it is used.
Thank you. Have you ever encountered a situation where the calculated mass fraction of organic matter in weathered coal exceeds 100%? With our potassium dichromate method, could there be some substances interfering with the results?