wtw PhotoLab S6 Operating Instructions Manual page 22

Instructions for the Preparation of Standard Solutions
Standard solution of bromine
acc. to DIN EN ISO 7393
Preparation of a KlO
In a 1000-ml volumetric flask dissolve 1.005 g
of KlO art.1.02404, in 250 ml of distilled water.
3,
Subsequently make up to the mark with distilled
water.
Preparation of a KlO
Transfer 8.90 ml of the KlO
1000-ml volumetric flask, add approx. 1g of Kl,
art. 1.05043, and make up to the mark with
distilled water.
1 ml of this solution is equivalent to 0.020 mg
of bromine.
Preparation of the bromine standard solution:
Pipette 10 ml KlO /Kl standard solution into a
3
100-ml volumetric flask, add 2.0 ml of H
0.5 mol/l, art. 1.09072, leave to stand for 1 min,
and then add NaOH 2 mol/l, art. 1.09136,
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
bromine.
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 bromine
standard solution remains stable for a maximum
of 5 minutes.
Reagents required:
1.02404.0100 Potassium iodate, volum. standard
1.05043.0250 Potassium iodide GR
1.09072.1000 Sulfuric acid 0.5 mol/l
1.09136.1000 Sodium hydroxide solution 2 mol/l
XX
stock solution:
3
/Kl standard solution:
3
stock solution to a
3
SO
2 4
3
Standard solution of free chlorine
Preparation of a stock solution of free chlorine:
First prepare a 1:10 dilution using a sodium hypo-
chlorite solution containing approximately 13 % of
active chlorine. For this pipette 10 ml of sodium
hypochlorite solution into a calibrated or confor-
mity-checked 100 ml volumetric flask and then
make up to the mark with DI water.
Precise assay of the stock solution for free
chlorine:
Pipette 10.0 ml of the stock solution into a 250 ml
ground-glass-stoppered conical flask containing
60 ml of DI water. Subsequently add to this solu-
tion 5 ml of hydrochloric acid 25% GR. and 3 g of
potassium iodide. Close the conical flask with the
ground-glass stopper, mix thoroughly, and leave to
stand for 5 min.
Titrate the eliminated iodine with sodium thiosul-
fate solution 0.1 mol/l until a weakly yellow colour
emerges. Add 2 ml of zinc iodide-starch solution
and titrate from blue to colourless.
Calculation:
1 ml sodium thiosulfate solution = 3.55 mg free
chlorine
Further investigational concentrations may be pre-
pared from the stock solution prepared according
to the procedure described above by diluting
/Kl
accordingly.
Stability:
When stored in a cool place (refrigerator), the
stock solution remains stable for approximately
one week. Further dilutions (investigational con-
centrations) are stable for approximately 2 hours.
Reagents required:
1.00316.1000 Hydrochloric acid 25 % GR
1.05614.9025 Sodium hypochlor. solution techn.
1.09147.1000 Sodium thiosulfate solution
1.05043.0250 Potassium iodide GR
1.05445.0500 Zinc iodide-starch solution GR
1.16754.9010 Water GR
approx. 13 % active chlorine
0.1 mol/l 0.1 N solution
Release 07/03