Release 06/2014
Spectroquant
®
photometers NOVA 60 and Pharo photometers
Instructions for the Preparation of Standard Solutions
Standard solution of free chlorine
Preparation of a stock solution:
First prepare a 1:10 dilution using a sodium hypochlorite solution con-
taining approx. 13% of active chlo rine. 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 distilled water.
Precise assay of the stock solution:
Pipette 10.0 ml of the stock solution into a 250-ml ground-glass-
stoppered conical flask containing 60 ml of distilled water. Subsequently
add to this solu tion 5 ml of hydrochloric acid 25% and 3 g of potassium
iodide. Close the conical flask with the ground-glass stopper, mix thor-
oughly, and leave to stand for 1min.
Titrate the eliminated iodine with sodium thiosul fate solution 0.1 mol/l
until a weakly yellow color emerges. Add 2 ml of zinc iodide-starch solu-
tion and titrate from blue to colorless.
Calculation and preparation of a standard solution:
Consumption of sodium thiosulfate solution 0.1 mol/l (ml) x 355 =
= content of free chlorine, in mg/l
Further investigational concentrations may be prepared from the stock
solution prepared according to the procedure described above by di-
luting accordingly with distilled water.
Stability:
When stored in a cool place (refrigerator), a standard solution remains
stable for approx. one week. The diluted standard solutions (investi-
gational concentrations) are stable for approx. 2 hours.
Note:
This is a standard solution that is absolutely necessary for the prepa-
ration of the monochloramine standard.
Reagents required:
1.00316.1000 Hydrochloric
acid 25 %
for analysis
EMSURE
®
1.05614.9025 Sodium hypo-
chlorite solution
techn. approx.
13% active
chlorine
1.09147.1000 Sodium thio-
sulfate solution
0.1 mol/l
Titripur
®
1.05043.0250 Potassium
iodide GR for
analysis
1.05445.0500 Zinc iodide-
starch solution
GR for analysis
1.16754.9010 Water for
analysis
EMSURE
®
Standard solution of total chlorine
Preparation of a standard solution:
Dissolve 4.00 g of chloramine T GR with distilled water in a calibrated or
conformity-checked 1000-ml volu metric flask and make up to the mark
with distilled water.
The standard solution prepared according to this procedure has a con-
centration of 1000 mg/l total chlorine.
Further investigational concentrations may be prepared from this stan-
dard solution by diluting accordingly with distilled water.
Stability:
When stored in a cool place (refrigerator), the standard solution of
1000 mg/l and the diluted standard solutions (investigational concen-
trations) remain stable for one day.
Reagents required:
1.02426.0250 Chloramine T
trihydrate GR
for analysis
1.16754.9010 Water for
analysis
EMSURE
®
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