Weigh 1g (accurate to 0.001 g) sample at room temperature, place it in a 250 mL stoppered Erlenmeyer flask, add 25 mL of ethanol, cover the stopper, and shake it on the shaker. Oscillate at low speed for 1 h, then add 100 mL of distilled water, shake well, filter, and collect the filtrate.
18.104.22.168.2 Pipette 0.5 mL 22.214.171.124, 1 filtrate into 50 mL volumetric flask, use Dilute the distilled water to the mark and mix to obtain the diluted solution.
126.96.36.199.3 Pipette 5, 188.8.131.52 of the dilution 10 mL in a 50 mL Erlenmeyer flask, add 2.0 mL. 20% sulfuric acid, shake l min. Then use a 200 pL micropipette to add 50 μL of 0.01 mol / L potassium permanganate solution, while adding potassium permanganate solution. Start the stopwatch to oscillate, stop the timing when the purple color of the solution completely disappears. The time (in seconds) elapsed from the complete disappearance of the magenta of the recording solution, that is, the oxidation time of the sample. Each sample was measured in parallel three times, and the arithmetic mean value was taken as the measured value of the sample.