1. Preface

Ammonium sulfate is an inorganic substance, a colorless crystal or white granule, and odorless. Ammonium sulfate is mainly used as a fertilizer and is suitable for various soils and crops. It can also be used in textile, leather, medicine and other fields. As most of its production methods are neutralization methods, drying treatment is required at the end. Eventually, moisture detection will be conducted to determine the quality of the finished product.

This method, by using the JH-V3 Karl Fischer moisture titrator (volumetric method), can quickly detect the moisture in ammonium sulfate. It is convenient and fast, has good data repeatability and accurate results. It is the best choice for moisture detection of this type of product.

2 Instruments and equipment

2.1 Instruments

JH-V3 Karl Fischer moisture titrator (volumetric method), double platinum electrodes, 5mL titration unit.

2.2 Reagents

Karl Fischer titrant two-component.

3 Experimental Methods

3.1 Experimental Procedures

Weigh 5.0g of the sample and place it in a 250mL conical flask with a rubber stopper. Use a large pipette to measure 50mL of anhydrous methanol solution. Cover the flask with the stopper, shake thoroughly for 5 minutes, let it stand for 10 minutes, and wait for the sample to settle. Use a pipette to draw 1mL of the upper methanol extract. When the instrument is in standby mode, click on the system injection, quickly add the titration cell through the liquid addition port, immediately cover the rubber stopper, click "Start Measurement", and use Karl Fischer. Titrate the titrant to the endpoint and record the volume V1 consumed.

Titrate 1mL of anhydrous methanol in the same way and record the volume V2 of the consumed Karl Fischer titrant.

3.2 Instrument Parameters

4 Results and Discussion

4.1 Experimental Results

 Calculation formula:

In the formula:

X - represents the moisture content of the sample (%);

V1 - The volume (mL) of titration liquid consumed when titrating the sample; m - The weighing amount of the sample (g);

T - represents the concentration of the titrant (mg/mL).

4.2 Conclusion and Discussion

The moisture content of ammonium sulfate was determined by the JH-V3 Karl Fischer moisture titrator (volumetric method). The data repeatability was good, and the absolute difference between the two groups of data did not exceed 0.05% as required by GB/T 535-2020. The detection method was simple and easy to operate, and could meet the daily production detection requirements.

References

[1] General Principles of the Chinese Pharmacopoeia 2020 Edition, Part IV, Karl. Fischer moisture determination method.

[2]GB/T 535-2020 Fertilizer Grade Ammonium Sulfate.