Release 06/2014
Spectroquant
®
photometers NOVA 60 and Pharo photometers
Instructions for the Preparation of Standard Solutions
Standard solution of sulfite
Preparation of a stock solution:
Dissolve 1.57 g of sodium sulfite and 0.4 g of Titriplex
®
III GR with dis-
tilled 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 approx. 1000 mg/l sulfite.
Precise assay of the stock solution:
Place 50.0 ml (full pipette) of the sulfite stock solution and 5.0 ml (full
pipette) of hydrochloric acid 25 % in a 300-ml conical flask.
To this solution add 25.0 ml (full pipette) of iodine solu tion 0.05 mol/l and
process immediately. After mixing the contents of the flask, subsequent-
ly titrate with sodium thiosulfate solution 0.1 mol/l until the yellow iodine
color has disappear ed, add 1 ml of zinc iodide-starch solution, and con-
tinue to titrate from blue to colorless.
Calculation and preparation of the standard solution:
C1 = consumption of sodium thiosulfate 0.1 mol/l (ml)
C2 = quantity of iodine solution 0.05 mol/l (25.0 ml)
mg/l sulfite = (C2 – C1)
x 80.06
Further investigational concentrations may be prepared from the stock
solution exactly deter mined according to the procedure described above
by diluting accordingly with distilled water and buffer solution pH 9.00.
This is done in the following manner:
Withdraw the desired aliquot from the stock solution, place in a cali-
brated or conformity-approved 1000-ml volumetric flask, add 20 ml of
buffer solution pH 9.00, make up to the mark with distilled water, and
mix.
Stability:
When stored in a cool place (refrigerator), the stock solution of approx.
1000 mg/l remains stable for at most one day. The diluted standard solu-
tions (investigational concentrations) must be used immediately.
Reagents required:
1.06657.0500 Sodium sulfite
anhydrous
for analysis
EMSURE
®
1.08418.0100 Titriplex
®
III GR
for analysis
1.09099.1000 Iodine solution
0.05 mol/l
Titripur
®
1.09147.1000 Sodium thio-
sulfate solution
0.1 mol/l
Titripur
®
1.00316.1000 Hydrochloric
acid 25 % GR
for analysis
EMSURE
®
1.05445.0500 Zinc iodide-
starch solution
GR for analysis
1.09461.1000 Buffer solution
pH 9.00
Certipur
®
1.16754.9010 Water for
analysis
EMSURE
®
To Next Page
Loading...