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2025
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Determination of iodide content in table salt by fully automated potentiometric titration
1. Introduction
Appropriate consumption of iodized salt can prevent goiter, but excessive intake can lead to diseases such as hyperthyroidism. Therefore, determining the iodine content in iodized salt is crucial.
This method uses the JH-T6 fully automatic potentiometric titrator from Shanghai Jiahang. According to the determination method of iodate in GB/T 13025.7-2012, sodium thiosulfate is used to directly titrate the iodate ion and elemental iodine oxidized by potassium iodide under acidic conditions to determine the iodine content in iodate. The results are more accurate than manual titration, and the titration speed is faster, reducing the influence of iodine volatilization on the experiment, providing a more reliable experimental basis for the determination of iodine content in iodized salt.
2. Instruments and Equipment
2.1 Instruments
JH-T6 fully automatic potentiometric titrator, platinum composite electrode.
2.2 Reagents
Sodium thiosulfate solution (0.02 mol/L), potassium iodide solution (50 g/L), phosphoric acid (1 mol/L).
3 Experimental Methods
3.1 Experimental Procedure
Weigh approximately 10 g of salt, accurate to 0.001 g, dissolve in 50 ml of distilled water. Add 2 ml of phosphoric acid solution (1 mol/L) and 5 ml of potassium iodide solution (50 g/L) using a pipette. Titrate to the endpoint with standardized sodium thiosulfate solution (0.02 mol/L). Perform a blank test simultaneously.
3.2 Parameter Settings
4. Results and Discussion
4.1 Experimental Results
Blank volume: 0.521
Calculation formula:
In the formula:
w -- Mass fraction of iodine in the sample, in milligrams per kilogram (mg/Kg);
126.90 -- Molar mass of iodine, in grams per mole (g/mol);
C(Na₂S₁₂O₃) -- Concentration of sodium thiosulfate solution, in moles per liter (mol/L);
V₀ -- Volume of sodium thiosulfate solution consumed in the blank titration, in milliliters (mL);
V₁ -- Volume of sodium thiosulfate used in the titration (mL);
m -- Mass of the sample, in grams (g);
1000 -- Volume conversion factor.
4.2 Spectra
4.3 Conclusion
The measurement results show good repeatability, with a clear endpoint, making it easy to determine the titration endpoint. It can accurately determine the iodine content of iodate in table salt.
References
[1] GB/T 13025.7-1999 General Test Methods for Salt Industry – Determination of Iodine. [S]
Keyword:
Automated potentiometric titration
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