XXV
Release 07/03
Instructions for the Preparation of Standard Solutions
Standard solution sulfite
Preparation of a standard solution:
Dissolve 1.57 g of sodium sulfite GR and 0.4 g of
Titriplex III GR. with DI water in a calibrated or
conformity-checked 1-l volumetric flask and make
up to the mark. The stock solution prepared
according to this procedure has a concentration of
1000 mg/l sulfite.
Further investigational concentrations may be
prepared from this stock solution by diluting
accordingly.
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Stability:
When stored in a cool place (refrigerator), the
stock solution remains stable for only one day
▼
Reagents required:
1.06657.0500
Sodium sulfite GR
1.08418.0100
Titriplex III GR
1.16754.9010
Water GR
Standard solution of a-surfactants
Preparation of a standard solution:
Dissolve 1.00 g of sodium 1-dodecanesulfonate
with DI water in a calibrated or conformity-
checked 1-l volumetric flask and make up to the
mark. The stock solution prepared according to
this procedure has a concentration of 1000 mg/l
anionic surfactants.
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. The
diluted investigational solutions must be used
immediately.
▼
Reagents required:
1.12146.0005
Sodium 1-dodecanesulfonate
1.16754.9010
Water GR
Standard solution of sulfide
Preparation of a stock solution:
Place 7.2 g of glass-clear, if necessary washed
crystals of sodium sulfide hydrate approx. 35 %
GR in a calibrated or conformity-checked
1-l volumetric flask, dissolve with DI water, and
make up to the mark. The stock solution prepared
according to this procedure has a concentration
of approx. 1000 mg/l sulfide.
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Precise assay of the standard solution (stock
solution) for sulfide:
Place 100 ml of DI water and 5 ml (full pipette) of
sulfuric acid 25 % GR in a 500 ml ground-glass
conical flask. To this solution add 25.0 ml (full
pipette) of the sulfide stock solution of approx.
1000 mg/l and 25.0 ml (full pipette) of iodine solu-
tion 0.05 mol/l. Shake the contents of the flask
thoroughly for about one minute, subsequently
titrate with sodium thiosulfate solution 0.1 mol/l
until the yellow iodine colour has disappeared,
add 1 ml of zinc iodide-starch solution, and con-
tinue to titrate until a milky, pure white colour
emerges.
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Calculation of the exact content of the sulfide
solution:
C1 = consumption of sodium thiosulfate 0.1 mol/l
C2 = quantity of iodine solution 0.05 mol/l (25.0 ml)
mg/l sulfide = (C2 – C1)
x
64,1026
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 remains stable for at most one day.
The further diluted solutions (investigational
concentrations) must be used immediately.
▼
Reagents required:
1.09099.1000
Iodine solution 0.05 mol
I2/l 0.1 N solution
1.06638.0250
Sodium sulfide hydrate approx.
35 % GR
1.09147.1000
Sodium thiosulfate solution
0.1 mol/l 0.1 N solution
1.00716.1000
Sulfuric acid 25 % GR
1.05445.0500
Zinc iodide-starch solution GR
1.16754.9010
Water GR
