1 Oxygen Consumption
1.1 Acidic Potassium Permanganate Titration Method
1.1.1 Scope
This Standard specifies determination of oxygen consumption in drinking water and its source water by acidic potassium permanganate titration method.
This method is applicable to the determination of oxygen consumption in drinking water and its source water whose chloride mass concentration is less than 300mg/L (counted in Cl-).
For the purpose of this method, the minimum detectable mass concentration (taking 100mL water sample) is 0.05mg/L and the maximum determinable oxygen consumption is 5.0mg/L (counted in O2).
1.1.2 Principle
Potassium permanganate oxidizes the reducing substances in acid solution and excess potassium permanganate is reduced with oxalic acid. The oxygen consumption is represented according to potassium permanganate consumption (counted in O2).
1.1.3 Apparatus
1.1.3.1 Electric-heated thermostatic water bath (may be adjusted to 100℃).
1.1.3.2 Conical flask: 100mL.
1.1.3.3 Burette.
1.1.4 Reagents
1.1.4.1 Sulfuric acid solution (1+3): slowly add 1 volume of sulfuric acid (ρ20=1.84g/mL) to 3 volumes of pure water under cooling in water bath, boil and add potassium permanganate solution in a dropwise way until the solution keeps in reddish color.
1.1.4.2 Standard stock solution of sodium oxalate : weigh 6.701g sodium oxalate (Na2C2O4), dissolve it in a small amount of pure water, scale the volume with pure water in a 1000mL volumetric flask. Keep it at a dark place.
1.1.4.3 Potassium permanganate solution : weigh 3.3g potassium permanganate (KMnoO4), dissolve it in a small amount of pure water and dilute to 1000mL. Boil for 15min, keep it still for 2W. Then, filter with glass sand core funnel into a brown bottle, keep at a dark place and calibrate the concentration according to the following method:
1.1.4.3.1 Pipet 25.00mL sodium oxalate solution (1.1.4.2) in a 250mL conical flask, add 75mL newly-boiled and cooled pure water and 2.5mL sulfuric acid (ρ20=1.84 g/mL).
1.1.4.3.2 Add about 24mL potassium permanganate solution from the burette rapidly; after fading, heat to 65℃ and continue titration until it is reddish and maintains for 30s. At the end of the titration, solution temperature is not less than 55℃. Record the consumption of potassium permanganate solution.
Calculation for concentration of potassium permanganate solution is detailed in Formula (1):
Foreword I
1 Oxygen Consumption
2 Biochemical Oxygen Demand
3 Petroleum
4 Total Organic Carbon
