Before performing a membrane electrode DO test, the zero calibration uses a reading on a sample containing an excess of _____ and a trace of cobalt chloride, CoCl2.

Before performing a membrane electrode DO test, the zero calibration uses a reading on a sample containing an excess of _____ and a trace of cobalt chloride, CoCl2.

• A. Sodium Chloride
• B. Sodium Sulfite
• C. Potassium Permanganate
• D. Magnesium Sulfate

Answer: (B)