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The content of sodium sulfite in wastewater was determined by fully automatic potentiometric titrati

July 04, 2025

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1 Preface

Sodium sulfite is a small white or yellow granule, generally used as a reducing agent. In wastewater treatment, it can reduce toxic heavy metals and also has a bactericidal effect. Sodium sulfite is also used in the water treatment industry as a deoxidizer for boiler water, industrial water, as well as an antioxidant and preservative. The content of sodium sulfite in wastewater was determined by potentiometric titration.

2. Instruments and equipment

2.1 Instruments

JH-T6 fully automatic potentiometric titrator, platinum composite electrode

2.2 Reagents

Iodine solution (0.1mol/L), hydrochloric acid (1+ 1), sodium thiosulfate titrant (0.1mol/L)

3 Experimental Methods

3.1 Experimental Procedures

Weigh approximately 0.08g of the sample into a titration cup, and accurately add 25mL of iodine solution (0.1mol/L) and 2mL of salt using a pipette

Mix 1+ 1 acid solution with 30mL of water, seal the seal and shake slowly until the sample dissolves. Then place it in the dark for 5 minutes. Then titrate to the endpoint with sodium thiothiate standard titration solution.

3.2 Parameters

Titration mode:		Dynamic titration
Electrode equilibrium time: 4 seconds		Pre-stirring time: 6 seconds
Electrode equilibrium potential: 1mv		Titration speed: standard

Minimum addition volume: 0.02mL		Pre-titration addition volume
Final volume: 30mL		pre-titration stirring time: 8 seconds
Potential spike: 500		Pre-controlled mv value: none

4. Results and Discussion

4.1 Experimental Results

Blank volume: 25.943mL

Sample name	Sample weight （ g ）	Titration volume （ mL ）	Sodium sulfite content （ % ）	Average value （ % ）
Wastewater	0.08956	13.285	88.71	88.71
	0.08711	13.631	88.72
	0.08742	13.581	88.76
	0.09101	13.088	88.66

Calculation formula

In the formula:

X - The content of sodium sulfite in the sample, with the unit of (%);

C - The concentration of sodium thiosulfate solution, measured in moles per liter (mol/L); V0 - The volume of sodium thiosulfate solution consumed for blank use, measured in milliliters (mL);

V1 - The volume of sodium thiosulfate solution consumed by the sample, in milliliters (mL); M - The molar mass of sodium sulfite, measured in grams per mole (g/mol);

m - The mass of the sample, with the unit of (g);

4.2 Atlas

4.3 Conclusion

In this paper, the content of sodium sulfite in wastewater was determined by potentiometric titration. The experimental data show that the T960 potentiometric titrator has good repeatability and can meet the needs of the analysis work.

Precautions

Sodium thiosulfate and iodine solution should be kept away from light.