Using potassium dichromate
Most commonly, a 0.25 N solution of potassium dichromate is used for COD determination, although for samples with COD below 50 mg/L, a lower concentration of potassium dichromate is preferred.
What is the oxidizing agent used in the COD measurement?
The COD is often measured using a strong oxidant (e.g. potassium dichromate, potassium iodate, potassium permanganate) under acidic conditions.
Why potassium dichromate is used in COD?
Currently, most COD tests use potassium dichromate as the oxidant. ... During the digestion, it's necessary to have excess oxidant; this ensures complete oxidation of the sample. As a result, it's important to determine the quantity of excess oxidant. The two most common methods for this are titration and colorimetry.
