Method ID: HI0003EN
0.1M Sodium Thiosulfate Titrant Concentration
Titrator Application Methods: General Methods - r. 2.3
Description:
Method for the standardization (titer determination)
of 0.1M Sodium Thiosulfate (Na
2
S
2
O
3
) titrant
solution, against Potassium Iodate (KIO
3
). The
results are expressed in M (mol/L).
Reference:
Adaptation of AOAC Official Methods of Analysis,
Official Method 942.27
Electrode:
HI 3131B Combination ORP Electrode
Reagents:
HI 70439 0.1M Sodium thiosulfate solution (1 L)
HI 70407 Potassium Iodate (20 g)
HI 70425 16% Sulfuric Acid (500 mL)
HI 70468 Potassium Iodide (35 g)
HI 70436 Distilled Water (1 gal)
Accessories:
HI 70300L Storage Solution (500 mL)
HI 7071 Electrode Fill Solution (4*30 mL)
Analytical Balance with a minimum resolution of
0.0001g is recommended
150-mL Glass Beakers
100-mL Class-A Volumetric Flask
10-mL Class-A Volumetric Pipette
Procedure:
Connect the ORP probe to the titrator.
Press “Select Method” from the main screen. Use
the arrow keys to highlight „HI0003EN 0.1M
Na2S2O3 Titr. Conc.‟ and press “Select”.
Install a 25-mL burette with 0.1M sodium
thiosulfate solution (HI 70439) on pump-one and
verify that no air bubbles are present in the burette
or tubing. If necessary prime until all air has been
removed completely.
Crush approximately 2 grams of potassium iodate
(HI 70407) and dry it for 2 hours at 120°C. Cool to
room temperature in a desiccator.
Weigh 0.35 g of dried potassium iodate with an
accuracy of 0.0001 g. Transfer the salt to a 100-
mL volumetric flask. Add approximately 80 mL of
distilled water and mix. Dissolve completely before
bringing to volume.
Use a class-A volumetric pipette to transfer
exactly 10.00 mL of prepared standard solution to
a 150-mL glass beaker and add distilled water to
the 100-mL mark on the beaker.
To the beaker add 5 mL of 16% sulfuric acid (HI
70425) and 1.5 g of potassium iodide (HI 70468).
Place the beaker under the stirrer assembly and
immerse the ORP electrode and stirrer. Ensure
that the reference junction of the ORP electrode is
5-6 mm below the surface. If necessary add extra
distilled water.
Press “Start”. You will be prompted to enter the
analyte size (weight of KIO
3
). Use the numeric
keypad to enter the exact weight and press
“Enter” to start the analysis.
At the end of the titration, after detection of the
equivalence point, „titration completed‟ will appear
with the titrant concentration. The result is
expressed in M (mol/L) of sodium thiosulfate.
Remove the electrode and stirrer from the sample
and rinse them thoroughly with distilled water.
Record the result (titer concentration).
NOTE: For optimal accuracy repeat this procedure a
minimum of three times and calculate the mean
value.
For methods utilizing 0.1N Na
2
S
2
O
3
titrant
solution, follow the steps below to enter the
titer/standardized value.
Select the method utilizing 0.1N Na
2
S
2
O
3
.
Select „Method Options‟ from the main screen.
Using the arrow keys, highlight „Titrant Conc.‟ and
press “Select”.
Use the numeric keypad to enter the standardized
(titer) value of the titrant then press „Accept‟.
Press „Escape‟ to exit the Method Options screen
and select „Save Method‟ option.
Method Parameters:
Name: 0.1M Na2S2O3 Titr. Conc.
Method Revision: 2.3
Titration Type: Standard Titration
Analog Board: Analog 1
Stirrer Configuration: Stirrer 1
Pump Configuration:
Titrant Pump: Pump 1
Dosing Type: Dynamic
min Vol: 0.030 mL
max Vol: 0.600 mL
delta E: 6.500 mV
End Point Mode: mV 1EQ point, 1st Der.
Recognition Options:
Threshold: 50 mV/mL
Range: No
Filtered Derivatives: No
Pre-Titration Volume: 5.000 mL
Pre-Titration Stir Time: 0 sec
Measurement Mode: Signal Stability
delta E: 0.3 mV
delta t: 2.0 sec
t-min wait: 2 sec
t-max wait: 20 sec
Electrode Type: ORP
Blank Option: No Blank
Calculations: Stdz. Titrant by Weight
Dilution Option: Enabled
Final Dilution Volume: 100.000 mL
Aliquot Volume: 10.000 mL
To Next Page
Loading...
