I would like to determine COD value through dichromate method.

But There is so many titrimetric method not colorimetric....

May I ask you how to do the colorimetric dichromate method..?

This is colorimetric method i found but I couldn't find in detail (concentration of solution) anymore...

•Switch on dry-block heater on 150℃

•Preparing Samples

-Deionized water as reference blanks of 2.5mL in digestion vessel

-Blend and mix the water samples before pouring any volume

•2.5mL of water sample into digestion vessel

•1.5mL of digestion solution (K2Cr2O7) to each digestion vessel

•3.5mL of sulfuric acid •Mix and Starting the dry-block heater on 150℃ for 2hr

Thank you for reading