wtw PhotoLab Spektral Operating Instructions Manual page 26

Instructions for the Preparation of Standard Solutions
Standard solution of hydrogen peroxide
Preparation of a stock solution:
Place 10 ml of Perhydrol 30 % H
calibrated or conformity-checked 100-ml
volumetric flask and make up to the mark with
distilled water. Transfer 30 ml (full pipette) of this
solution to a calibrated or conformity-checked
1000-ml volumetric flask and make up to the mark
with distilled water. The stock solution prepared
according to this procedure has a concentration
of approximately 1000 mg/l hydrogen peroxide.
Precise assay of the standard solution (stock
solution) for hydrogen peroxide:
Pipette 50.0 ml (full pipette) of the hydrogen per-
oxide stock solution of approx. 1000 mg/l into a
500-ml conical flask, dilute with 200 ml of distilled
water, and add 30 ml of sulfuric acid 25 % GR.
Titrate with a 0.02 mol/l potassium permanganate
solution until the colour changes to pink.
Calculation of the exact content of the
hydrogen peroxide concentration:
Consumption of potassium permanganate (ml)
34.02 = content of hydrogen peroxide, in mg/l
x
Further investigational concentrations may be pre-
pared from the stock solution exactly determined
according to the procedure described above by
diluting accordingly.
Stability:
When stored in a cool place (refrigerator), the
stock solution and the further diluted investiga-
tional solutions remain stable for one day.
Reagents required:
1.09122.1000 Potassium permanganate solution
0.02 mol/l 0.1 N
1.07209.0250 Perhydrol 30 % GR for analysis
1.00716.1000 Sulfuric acid 25 % GR for analysis
1.16754.9010 Water GR for analysis
XXIV
O GR in a
2 2
Standard solution of iodine
acc. to DIN EN ISO 7393
Preparation of a KlO
3
Dissolve 1.005 g of KlO
water in a calibrated or conformity-checked
1000-ml volumetric flask. Subsequently make up
to the mark with distilled water.
Preparation of a KlO /Kl standard solution:
3
Transfer 5.60 ml of the KlO
calibrated or conformity-checked 1000-ml
volumetric flask, add approx. 1g of Kl and make
up to the mark with distilled water.
1 ml of this solution is equivalent to 0.020 mg
of iodine.
Preparation of the iodine standard solution:
Pipette 10 ml KlO /Kl standard solution into a
3
calibrated or conformity-checked 100-ml
volumetric flask, add 2.0 ml of H
leave to stand for 1 min, and then add NaOH 2
mol/l dropwise (approx. 1 ml) until the solution
just loses its colour. Subsequently make up the
solution to the mark with distilled water.
The concentration of the solution is 2.00 mg/l
iodine.
Stability:
The KlO stock solution remains stable for 4
3
weeks when stored in a cool place. The KlO
standard solution can be used for 5 hours when
stored in a cool place. The dilute iodine standard
solution is not stable and must be used
immediately.
Reagents required:
1.02404.0100 Potassium iodate, volum. standard
1.05043.0250 Potassium iodide GR for analysis
1.09072.1000 Sulfuric acid 0.5 mol/l
1.09136.1000 Sodium hydroxide solution 2 mol/l
1.16754.9010 Water GR for analysis
stock solution:
in 250 ml of distilled
3
stock solution to a
3
SO 0.5 mol/l,
2 4
/Kl
3
Release 05/04