GB/T 3521-2023Methods for chemical analysis of graphite (English PDF)

5.1 Instruments, Equipment and Materials

5.1.2 Analytical balance. with an accuracy not lower than 0.1 mg.

5.1.3 Ground-mouth weighing bottle. 20 mL. […]

5.2 Analytical Procedures

5.3 Result Calculation

The mass fraction (w1) of moisture is calculated in accordance with Formula (1).

5.4 Allowable Deviation

The absolute difference between the results of two parallel determinations shall not be greater than 0.05%.

6.1 Box-type High-temperature Furnace Method

6.1.1 Method summary

When the specimen is burned at a high temperature, the amount of volatile substance decomposed and escaped is the volatile matter.

6.1.2 Instruments, Equipment and Materials

6.1.3 Analytical procedures

Accurately weigh-take 1 g of specimen, accurate to 0.1 mg, and record it as m2. Evenly lay it on the bottom of the double-covered porcelain crucible with a constant weight. Place the crucible on the crucible holder, put on the double cover, and place it in the box-type high-temperature furnace (constant-temperature zone).

6.1.4 Result calculation

The mass fraction (w2) of volatile matter is calculated in accordance with Formula (2).

6.1.5 Allowable deviation

The allowable deviation of the results of two parallel determinations is shown in Table 1.

6.2 Nitrogen Protection Method

6.2.1 Method summary

When the specimen is placed in a nitrogen flow and burned at a high temperature, the amount of volatile substance decomposed and escaped is the volatile matter.

6.2.2 Instruments, Equipment and Materials

6.2.2.1 Analytical balance. with an accuracy not lower than 0.1 mg.

6.2.2.4 Quartz boat. the sample loading volume is not less than 1 g.

6.2.2.5 Nitogen. high-purity nitrogen (mass fraction. 99.995%) can be used directly; pure nitrogen (mass fraction. 99.9%) needs to be purified before use.

6.2.4 Result calculation

The mass fraction (w3) of volatile matter is calculated in accordance with Formula (3).

6.2.5 Allowable deviation

The allowable deviation of the results of two parallel determinations is shown in Table 2.

7.1 Method Summary

When the specimen is burned at a high temperature, the residue obtained after the graphite oxidation products and volatiles completely escape is ash content.

7.2 Instruments, Equipment and Materials

7.2.1 Analytical balance. with an accuracy not lower than 0.1 mg.

7.2.4 Desiccator. equipped with color-changing silica gel.

7.3 Analytical Procedures

In accordance with the fixed carbon content, accurately weigh-take 1 g ~ 100 g of dried specimen (accurate to 0.1 mg) and record it as m8. Place it in a porcelain ark with a constant weight, put the porcelain ark into the box-type high-temperature furnace.

7.4 Result Calculation

The mass fraction (w4) of ash content is calculated in accordance with Formula (4).

7.5 Allowable Deviation

The allowable deviation of the results of two parallel determinations is shown in Table 3.

8.1 Indirect Carbon Determination Method

8.1.1 Method summary

The indirect carbon determination method is also called the combustion method, that is, after measuring the volatile matter and ash content of the specimen, they are subtracted from the total amount, and the difference is the fixed carbon content. This Method is applicable to graphite products with carbon content (mass fraction) greater than 50%.

8.1.2 Result calculation

8.1.2.1 The fixed carbon content (w5) of high, medium and low carbon graphite is calculated in accordance with Formula (5).

8.1.2.2 The fixed carbon content (w6) of high-purity graphite is calculated in accordance with Formula (6).

8.2 Direct Carbon Determination Method

8.2.2 Reagents

8.2.2.1 Hydrochloric acid solution (1 + 1).

8.2.2.2 Iron filing flux. the carbon content (mass fraction) is less than 0.0005%, and the sulfur content (mass fraction) is less than 0.0005%.

8.2.2.3 Tungsten particle flux. the carbon content (mass fraction) is less than 0.0008%, the sulfur content (mass fraction) is less than 0.0005%, and the particle size is 0.35 mm ~ 0.83 mm.

8.2.2.4 Graphite standard sample. graphite mineral composition analysis standard substance, GBW 03118, GBW 03119, GBW 03120.

8.2.2.5 Oxygen. with a purity not less than 99.5%.

8.2.3 Instruments, equipment and materials

8.2.3.1 High-frequency infrared carbon and sulfur analyzer. carbon determination accuracy is not less than 0.0001%.

8.2.3.2 Analytical balance. with an accuracy not lower than 0.1 mg.

8.2.3.6 Desiccator. equipped with color-changing silica gel.

8.2.3.7 Porcelain crucible. […]

8.2.6 Analytical procedures

8.2.6.1 Calibration test

Actuate the instrument and pre-heat for 30 minutes. Adjust the instrument to determine the fixed carbon state. Turn on the oxygen; in accordance with the sample to be determined, select the standard substance and perform system calibration, until the repeatability of the determination results reaches the uncertainty range required by the graphite standard sample. Thus, the system calibration test is completed.

8.2.6.2 Sample test

Add 0.5 g of iron filings flux and 1.5 g of tungsten particle flux into the crucible containing the treated specimen. Place the crucible on the quartz holder, number it, and click the "ANALYZE" button to start sample determination. The analysis time is adjusted in accordance with the CO2 release curve provided by the high-frequency infrared carbon and sulfur analyzer system. After the test is completed, in accordance with the data provided by the instrument, record the determination results.

8.2.7 Allowable deviation

The allowable deviation of the results of two parallel determinations is shown in Table 4.

9.1 Potassium Iodate Titration Method

9.1.2 Reagents

9.1.2.1 Hydrochloric acid solution (3 + 197).

9.1.2.2 Potassium iodate (KIO3). primary reagent.

9.1.2.3 Potassium iodide (KI). analytically pure.

9.1.2.4 Soluble starch. analytically pure.

9.1.2.5 Potassium iodate standard solution (0.0888 g/L). accurately weigh-take 0.0888 g of potassium iodate (KIO3) primary reagent and dissolve it in water. Transfer it to a 1,000 mL volumetric flask, dilute to the scale and store it in a brown bottle. 1 mL of this solution is equivalent to containing 0.04 mg of sulfur.

9.1.2.6 Starch-potassium iodide solution. weigh-take 2 g of soluble starch into 50 mL of water and make it into a paste. While stirring, add the paste to 150 mL of boiling water, boil it for 2 minutes. After cooling, add 6 g of potassium iodide (KI) and stir to dissolve it.

9.1.2.7 Sulfur standard sample. national standard substance of coke or coke whose sulfur content is determined using the Eschka method.

9.1.3 Instruments, equipment and materials

9.1.3.1 Analytical balance. with an accuracy not lower than 0.1 mg.

9.1.3.3 Sulfur determination device. see Figure 2.

9.1.3.4 Porcelain boat. the sample loading volume is not less than 1 g.

9.1.4 Analytical procedures

9.1.4.2 Specimen determination. add 2/3 volume of hydrochloric acid solution (3 + 197) into the sulfur determination cup, add 10 mL of starch-potassium iodide solution, and dropwise add potassium iodate standard solution to make the solution in the sulfur determination cup turn light blue. Use the same method to prepare a reference solution for judging the end point. Ventilate for 4 minutes ~ 5 minutes.

9.1.4.3 Determination of correction coefficient. in accordance with the sample content, select a coke standard sample with an appropriate sulfur content; accurately weigh-take 0.1 g ~ 1.0 g of standard sample, accurate to 0.1 mg, and record it as m11. In the burned porcelain boat, follow the subsequent steps in 9.1.4.2.

9.1.5 Result calculation

9.1.5.1 The correction coefficient (F) is calculated in accordance with Formula (7).

9.1.5.2 The sulfur content (w7) is calculated in accordance with Formula (8).

9.1.6 Allowable deviation

The allowable deviation of the results of two parallel determinations is shown in Table 5.

9.2 Combustion Titration Coulometry

9.2.1 Method summary

The specimen is burned and decomposed in the air flow under the action of a catalyst. The sulfur in the specimen generates sulfur oxides and is absorbed by the potassium iodide solution.

The iodine generated by electrolysis of potassium iodide solution is used for oxidative titration.

In accordance with the electricity consumed by electrolysis to generate iodine, calculate the total sulfur content in the specimen.

9.2.2 Reagents

9.2.2.1 Graphite standard sample. graphite mineral composition analysis standard substance, GBW 03118, GBW 03119, GBW 03120.

9.2.2.2 Tungsten trioxide. analytically pure.

9.2.2.3 Sodium hydroxide. analytically pure.

9.2.2.4 Potassium iodide. analytically pure.

9.2.3 Instruments, equipment and materials

9.2.3.1 Analytical balance. with an accuracy not lower than 0.1 mg.

9.2.3.2 Coal sample. with a particle size less than 0.3 mm, not less than 100 mg.

9.2.3.3 Color-changing silica gel.

9.2.3.4 Porcelain boat. bisque or corundum product; the length of the sample-holding part is about 60 mm, and the temperature resistance is greater than 1,200 °C.

9.2.3.5 Coulomb sulfur meter. it mainly consists of the following parts.

a) Tubular high-temperature furnace. it can be heated to above 1,200 °C. […]

9.2.4 Analytical procedures

9.2.4.2 Add 300 mL of electrolyte to the electrolytic cell and turn on the magnetic stirrer.

9.2.4.3 Turn on the electromagnetic pump, adjust the air flow to 1,000 mL/min, and check the air tightness.

9.2.5 Result calculation

The sulfur content (w8) in the specimen is calculated in accordance with Formula (9).

9.2.6 Allowable deviation

The allowable deviation of the results of two parallel determinations is shown in Table 6.

9.3 Infrared Absorption Spectrometry

9.3.1 Method summary

Place the specimen in a resistance furnace, under oxygen flow, burn it at a high temperature.

The sulfur is oxidized into sulfur dioxide gas. Utilize an infrared analyzer and an integration program to determine the total amount of sulfur dioxide generated. The instrument automatically calculates the sulfur content in the graphite.

9.3.2 Instruments, equipment and materials

9.3.2.3 Oxygen. with a purity of 99.5%.

9.3.2.4 Porcelain boat. the sample loading volume is not less than 1 g.

9.3.3 Analytical procedures

9.3.3.2 Blank test. place the empty porcelain boat in the center of the combustion furnace for testing. The test blank value shall not exceed 0.005%. […]