GB/T 535-2020Fertilizer grade ammonium sulphate (English PDF)

3.1 Appearance

White or off-white; powdery or crystalline; free from visible mechanical impurities.

3.2 Technical specifications

It shall comply with the requirements specified in Table 1, and shall also conform to the values indicated on the packaging container.

3.3 Limit requirements for toxic and hazardous substances

It shall comply with the requirements of Table 2.

4.1 Collection of composite samples

4.1.1 Bagged samples

4.1.1.1 When the total number of bags per batch does not exceed 512, the minimum number of bags to be sampled shall be determined in accordance with Table 3. When the total number of bags exceeds 512, the minimum number of bags to be sampled shall be determined based on the result calculated using formula (1). If the calculated result contains a decimal fraction, it shall be rounded up to the nearest integer. Where, n - Minimum number of sample bags; N - Total number of bags per batch.

4.1.1.2 When sampling, use a sampling probe to insert diagonally from one side of the bag opening to a depth of three-quarters of the bag's depth on the opposite side, so as to collect a representative sample. Collect a sample of no less than 0.1 kg from each bag. The total mass of the combined sample shall not be less than 2 kg.

4.1.2 Bulk samples

Sampling shall be conducted in accordance with the provisions of GB/T 6679.

Alternatively, cross-sectional samples may be collected from a belt conveyor - either randomly or at regular time intervals - using an automatic sampler, a scoop, or other suitable tools. The total mass of the composite sample collected for each batch shall not be less than 2 kg.

4.2 Sample reduction

Thoroughly and rapidly mix the combined sample. Reduce the sample size to approximately 1 kg using a sample divider or the quartering method, and then further divide it into two portions. Transfer these portions into two clean, dry glass or plastic bottles fitted with ground-glass stoppers. Seal and label the bottles, indicating the name of the manufacturer, product name, batch number (or production date), sampling date, and the name of the sampler. One bottle shall be used for product testing, while the other shall be retained for at least two months for reference purposes.

5.1 General provisions

Unless otherwise specified, the reagents and water used in this Standard refer to analytically pure reagents and Grade 3 water as specified in GB/T 6682. Unless the preparation method is explicitly indicated, all solutions shall be prepared in accordance with the provisions of HG/T 2843. With the exception of appearance, parallel determinations shall be performed on two test portions.

5.2 Appearance inspection

Visual Inspection.

5.3 Determination of nitrogen content

Determine in accordance with the method specified in Annex A.

5.4 Determination of sulfur content

Determine according to the method specified in NY/T 1117.

5.5 Determination of free acid content

Determine in accordance with the method specified in Annex B.

5.6 Determination of moisture content

Determine in accordance with the method specified in Annex C.

5.7 Determination of water-insoluble matter content

Determine in accordance with the method specified in Annex D.

5.8 Determination of chloride ion content

5.8.1 Method 1.Ion chromatography (reference method)

Weigh approximately 0.1 g of the specimen (accurate to 0.0002 g) and place it into a 50 mL volumetric flask. Add water to nearly 50 mL. Shake well. Allow to stand for a short while. Dilute to the mark with water. Shake well. Withdraw 10 mL of the supernatant and filter it through a 0.22 µm aqueous-phase filter membrane for purification.

Activate the barium (Ba) ion filtration column using 10 mL of ultrapure water. Allow it to stand for 10 min. Once fully equilibrated, take the aforementioned 10 mL of filtrate and slowly pass it through the barium (Ba) ion filtration column, controlling the flow rate so that it does not exceed 2 mL/min. Discard the first 2~3 mL. The remaining 6~7 mL constitutes the specimen solution for analysis. Subsequently, perform the determination in accordance with the method specified in GB/T 29400.

5.8.2 Method 2.Volhard method

Determine in accordance with the method specified in GB/T 24890.

5.8.3 Method 3.Automatic potentiometric titration

Determine according to the method specified in NY/T 1117.

5.9 Determination of fluoride content

5.9.1 Method 1.Ion chromatography (reference method)

Determine in accordance with Step 5.8.1.

5.9.2 Method 2.Ion-selective electrode method

Determine in accordance with the method specified in GB/T 32954.

5.10 Determination of thiocyanate ion content

Determine in accordance with Step 5.8.1.

5.12 Determination of total polycyclic aromatic hydrocarbons

6.1 Inspection categories and inspection items

Product inspection is classified into exit-factory inspection and type inspection. The items for exit-factory inspection include appearance, nitrogen content, free acid content, and moisture content. Type inspection includes all inspection items. Type inspection shall be conducted under any of the following circumstances.

- Following the commencement of formal production, shall there be significant changes to raw materials or manufacturing processes that may impact product quality specifications;

- During normal production operations, it shall be conducted either periodically or once a specific cumulative volume has been reached. The content of sulfur, water-insoluble matter, and chloride ions, as well as the parameters listed in Table 2, shall be inspected at least once every six months. The content of other toxic or hazardous substances shall be inspected at least once every two years;

- Upon the resumption of production following a prolonged suspension;

- Whenever type inspection is required by government regulatory authorities.

6.2 Batching

Products are inspected by batch. The maximum batch size is 150 tons or one day's production output.

6.3 Determination of results

6.3.1 In this Standard, the determination of conformity for product quality indicators shall be based on the "Rounding-off comparison method" specified in GB/T 8170. […]