Technical assistance: COD blank test
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The last edit to this post was made by hesonchang214 on 2012-12-7 at 22:01. Is the COD blank test related to temperature? I conducted several blank tests using the same reagents, but the blank value was as high as 28.4 ml – is COD related to temperature?
I really hadn’t thought of such issues; measuring COD is done by specialized laboratory technicians. However, according to the operating procedures, it is required that the boiled solution be fully cooled before performing the COD titration.
Theoretically, it shouldn’t matter, as COD is to be digested by heating; regardless of the room temperature, the temperature used for heating digestion remains constant, so there won’t be a significant difference in the intensity of the redox reactions.
What method did you use to measure it? The blank high mark I just created today is 23.3
It’s likely that the standard solution of your ammonium ferrous sulfate is inaccurate; it is recommended to recalibrate it using potassium dichromate and to adjust it with potassium hydrogen phthalate. Relevant methods are specified in national standards