What is oxygen consumption? Why is it an important indicator in down inspection and testing

▲ After shaking, the water was filtered through a standard sieve into a large beaker for later use.

At present, the detection methods of down oxygen consumption are basically the same at home and abroad.

First, take out 100ml of distilled water and 100ml of sample liquid with a measuring cylinder, place them in two Erlenmeyer flasks respectively, and then add 2mL of 3mol/L sulfuric acid to each. (Note: If the acidity is too high, potassium permanganate is easy to decompose, but if the acidity is too low, the reaction speed will be slow, and manganese dioxide will precipitate.

Sulfuric acid is commonly used to adjust the acidity of the solution. Nitric acid is oxidizing and should not be used; hydrochloric acid is reducing and will be oxidized by potassium permanganate and is not suitable for use. )

▲ Two flasks filled with sulfuric acid.

Then in 100mL of distilled water, add a drop of standard potassium permanganate solution of known concentration, as a blank sample for control; while in the filtered water of 100mL test sample, add a standard potassium permanganate solution of the same concentration drop by drop .

At the beginning of the titration, the reaction is slow, and the titration should be slow; as the manganese ions generated by the reaction increase, the reaction speed will be accelerated, and the titration speed can be accelerated accordingly, but still not too fast.

▲ blank sample for control

▲ Add the same concentration of standard potassium permanganate solution drop by drop.

Finally, when the filtered water of the sample also shows the same pink color as the blank sample, the oxygen consumption can be calculated by the volume of the consumed potassium permanganate solution.

The principle is that potassium permanganate solution has strong oxidizing ability in acidic environment, and its own color (pink), if it reacts with reducing substances, the color will fade, and the filtered water of the sample will not change color; if not Reaction occurs again, that is, oxygen is no longer consumed, and the potassium permanganate solution dissolves in water, turning the filtered water of the sample pink at the same time.

The above is the introduction about the oxygen consumption of down. If there are any omissions, readers are welcome to leave a message to supplement.