Determination of COD in hydrochloric acid
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There is waste hydrochloric acid, at about 30%, which contains certain organic substances; the COD is determined using an arbitration method. Yet the results of the two measurements for the same sample differ greatly. What is the reason?
This sample has too high a chlorine content, making it unsuitable for COD testing using the dichromate method, as chloride ions cause significant interference in COD determination. Adding a small amount of mercury sulfate can no longer effectively shield chloride ions. If possible, use hydrochloric acid of the same concentration as a control; after passing the sample through resin loaded with silver ions, remove the chloride ions and then determine the COD. Or choose an appropriate method to detect the organic compounds in the sample using the TOC method.