In COD analysis, which chemical is the primary oxidizing agent used to oxidize organic matter?

In COD analysis, which chemical is the primary oxidizing agent used to oxidize organic matter?

• A. Potassium Dichromate
• B. Ferrous Ammonium Sulfate
• C. Silver Nitrate
• D. Permanganate

Answer: (A)

In COD analysis, the key step is to chemically oxidize most of the organic matter in acidic solution, and the reagent that does this most reliably is potassium dichromate. It acts as the primary oxidizing agent, being reduced from hexavalent chromium (Cr(VI)) to Cr(III) as organics are oxidized. The amount of dichromate consumed reflects the oxygen equivalent of the organics, giving the COD value. Ferrous ammonium sulfate is used later as the titrant to determine how much dichromate remains, not to oxidize the organics itself. The other substances aren’t the primary oxidant in this method—perchlorates and silvers aren’t used as the main oxidant in COD, and while permanganate can oxidize organics, it’s used in a different COD procedure. So potassium dichromate is the correct choice because it is the reagent that directly oxidizes the organics in the standard COD test.

In COD analysis, the key step is to chemically oxidize most of the organic matter in acidic solution, and the reagent that does this most reliably is potassium dichromate. It acts as the primary oxidizing agent, being reduced from hexavalent chromium (Cr(VI)) to Cr(III) as organics are oxidized. The amount of dichromate consumed reflects the oxygen equivalent of the organics, giving the COD value. Ferrous ammonium sulfate is used later as the titrant to determine how much dichromate remains, not to oxidize the organics itself. The other substances aren’t the primary oxidant in this method—perchlorates and silvers aren’t used as the main oxidant in COD, and while permanganate can oxidize organics, it’s used in a different COD procedure. So potassium dichromate is the correct choice because it is the reagent that directly oxidizes the organics in the standard COD test.