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Analytical Procedures - Hydrogen Peroxide Concentration
December 20, 2001
Preparation of Glassware
Preparation of Hydrogen Peroxide Samples
The potassium permanganate method is commonly used to determine the concentration of hydrogen peroxide. A weighed sample is acidified and titrated with standard potassium permanganate solution until the first permanent pink colour persists for 30 seconds of longer.
5 H2O2 + 3 H2SO4 + 2 KMnO4 -> K2SO4 + 2 MnSO4 + 8 H2O + 5 O2
This method cannot be used when organic or inorganic matter that reduce potassium permanganate are present. Hydrochloric acid or other chloride ions are to be avoided as the permanganate will also oxidize chloride ions to chlorine and the titration will be subject to errors. The presence of fluoride ions affects the permanganate titration and large proportions of calcium salts or titanic acid lead to low results.
Use only new weighing vials and eye droppers
Treat new flasks overnight with 1:1 HNO3 at room temperature and rinse 6 to 8 times with water.
Do not use chromic acid cleaning solution on any glassware used for hydrogen peroxide testing. Trace chromium ions are excellent catalytic agents for decomposing peroxide and they are extremely difficult to remove from glassware.
Measure about 100 mL of water into a 250 mL Erlenmeyer flask
Add 10 mL of 1:4 vol/vol sulphuric acid
Draw about 1 mL of hydrogen peroxide sample into a standard eye dropper. Place the dropper into a specimen vial
Rapidly weigh and record the weight of the vial, dropper and hydrogen peroxide sample to (± 0.0002) g
Add 2 to 5 drops of the hydrogen peroxide sample from the dropper to the flash containing water and sulphuric acid. The number of drops is a function of the concentration of hydrogen peroxide according to the following:
H2O2 Concentration Number of Drops
30 wt% 5
35 wt% 4
50 wt% 3
70 wt% 2
Replace the dropper in the vial, rapidly re-weigh and record the new weight.
The sample weight will be the initial weight minus the final weight of the vial, eye dropper and sample.
Titrate with 0.10N KMnO4 while stirring constantly. As the end point is approached, add less KMnO4 until the titration progresses by fractional drop increments. The end-point is the first barely perceptible pink colour that persists for 30 seconds.
Estimate and record the volume of KMnO4 solution used to 0.01 mL. Apply a volume correction factor of ±0.1% per 5ºC deviation from 20ºC temperature.
Calculate the hydrogen peroxide concentration using:
% H2O2 = (mL x N x 0.01701 x 100) / (sample weight)