wtw PhotoLab S6 Operating Instructions Manual page 25

Instructions for the Preparation of Standard Solutions
Standard solution of COD
Preparation of a standard solution:
In a calibrated or conformity-checked 1-l volu-
metric flask make up 0.850 g of potassium
hydrogen phthalate GR volumetric standard to the
mark with DI water. The stock solution prepared
according to this procedure has a concentration of
1000 mg/l COD.
Further investigational concentrations may be
prepared from this stock solution by diluting
accordingly.
Stability:
When stored in a cool place (refrigerator), the
stock solution remains stable for one month.
When stored under appropriate cool conditions
(refrigerator), further investigational concentration
dilutions remain stable – depending on the respec-
tive concentration – for approximately one week to
one month.
Reagents required:
1.02400.0080 Potassium hydrogen phthalate GR
volumetric standard
1.16754.9010 Water GR
Standard solution of hydrazine
Preparation of a standard solution:
Dissolve 4.07 g of hydrazinium sulfate GR with
oxygen-low (boil previously) DI water in a cali-
brated or conformity-checked 1-l volumetric flask
and make up to the mark. The stock solution pre-
pared according to this procedure has a concen-
tration of 1000 mg/l hydrazine.
Further investigational concentrations may be
prepared from this stock solution 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:
1.04603.0100 Hydrazinium sulfate GR
1.16754.9010 Water GR
Release 07/03
Standard solution of iodine
acc. to DIN EN ISO 7393
Preparation of a KlO
3
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 /Kl standard solution:
3
Transfer 5.60 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 iodine.
Preparation of the iodine 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
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 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
stock solution:
stock solution to a
3
SO
2 4
/Kl
3
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