Finding the strength of Hydrogen Peroxide

 

Analytical methods
H2O2 concentration
General remarks
This method describes the determination of hydrogen peroxide concentration in an aqueous solution. We recommend that each sample is processed at least twice.

Procedure
Place approx. 50 ml 5 N sulfuric acid (H2SO4 , 2.5 mol/l ) in a flask and add an exactly weighed sample of the H2O2 containing solution. Use an analytical balance (four decimal digits). A syringe could be used to add the H2O2 sample. In this case, the syringe has to be rinsed thoroughly before use. Calculate the amount by weighing the filled syringe before and after adding a few drops to the flask.
For all procedures only deionized or distilled water should be used.

Titrate the sample with 0.25 N potassium permanganate solution (0.05 mol/l) while mixing vigorously. If using visual/manual titration, titrate until a pale pink coloration persists for a while. If using automatic titration equipment, the end point could be determined potentiometrically via a redox electrode.
Note: Potassium permangante solutions must be standardized regularly.

Calculation
The content of hydrogen peroxide in the solution is calculated as follows:


The result gives the concentration of hydrogen peroxide in the solution expressed in weight percent (g H2O2/100 g solution)
Stability
General remarks
This method describes the determination of hydrogen peroxide stability in an aqueous solution. A sample of hydrogen peroxide is stored at 96 °C for 16 hours. This treatment leads to a certain loss of hydrogen peroxide content. The percentage loss of content gives the decomposition rate of the sample.
The content of H2O2 before and after the treatment is analyzed with potassium permanganate in acidic medium.
Clean equipment and a clean workplace along with high purity of the reagents are essential for this analytical method. The flasks should be dedicated to this procedure. Otherwise, unreliable results could be obtained. We recommend that each sample is processed at least twice.

Procedure
Each of three flasks of 100 ml volume is filled with exactly 50 ml (pipette) of the hydrogen peroxide sample. To avoid losses by evaporation, the flasks are covered (e.g. with a condenser cap), but not closed tightly. One of the flasks is used to determine the initial hydrogen peroxide content. This one is stored at room temperature. The two other flasks are stored in a water bath for 16 hours at 96 °C. After that, all flasks are cooled to 20 °C and filled up to the 100 ml mark with distilled or deionized water. Now, the hydrogen peroxide content of these heated and unheated samples is determined. For this, the titration method with potassium permanganate is applied (see above).

Calculation
The decomposition rate of the hydrogen peroxide sample is calculated as follows:

pH value
General remarks
This method describes the determination of the apparent pH value of hydrogen peroxide. The measurement is carried out directly in the sample. A glass electrode and a common pH meter with a resolution of 0.01 pH units is used.
Procedure
The pH equipment must be calibrated for acidic pH ranges using two different, well-defined standard pH solutions. Calibration has to be repeated before every series of measurements.
Determination of the apparent pH of the hydrogen peroxide sample is carried out directly in the sample. The value given by the pH meter represents the final result.