GB/T 6609.7-2026Chemical analysis and physical property determination methods for alumina - Part 7: Determination of titanium dioxide, chromium sesquioxide, cupric oxide, fluorine, chlorine, boron trioxide, phosphorus pentoxide and sulfate - Spectrophotometry (English PDF)

4.2.6 Titanium Dioxide Standard Solution. Transfer

5.00 mL of titanium dioxide standard stock solution (4.2.5) to a 1000 mL volumetric flask and dilute with water. Dilute to the mark and mix well. 1 mL of this solution contains 5 µg of titanium dioxide.

4.3 Instruments and Equipment

4.3.1 Microwave digestion apparatus.

4.3.2 Spectrophotometer, absorption cell is 1cm or 5cm.

4.3.3 Oven. The temperature can be controlled at 300°C±10°C.

4.3.4 PTFE sealed sample container. See Figure A.1 in Appendix A for a schematic diagram.

4.4 Sample Sampling shall be carried out in accordance with the provisions of Chapter 6 of GB/T 6609.22-2026, and sample preparation shall be carried out in accordance with Section

7.4 of GB/T 6609.22-2026. The regulations shall be followed.

4.5 Test Procedure

4.5.1 Sample Weigh the sample (4.4) according to Table 2, accurate to 0.0001g.

4.5.2 Parallel Tests Perform two parallel experiments and take the average value.

4.5.3 Blank Test A blank test was performed along with the sample.

4.5.4 Measurement

4.5.4.1 Perform sample dissolution according to one of the following steps.

---PTFE sample dissolution method. Place the sample (4.5.1) in a sealed PTFE sample dissolution container (4.3.4), and when the sample mass... When the sample mass is 0.50g, add 10.0mL of hydrochloric acid (4.2.2); when the sample mass is 1.00g, add 15.0mL of hydrochloric acid (4.2.2). 2) Melt in an oven at 240°C±3°C (4.3.3) for 4 hours, then remove and cool;

---Microwave digestion method. Place the sample (4.5.1) in a reaction vessel of a 100mL microwave digester (4.3.1), and add 10.0mL of sulfur. Add acid (4.2.1), cover the reaction vessel, place it in the microwave digester, and proceed with the selected optimal microwave digestion program. Dissolve.

4.5.4.2 Preparation of test solution. Rinse the solution (4.5.4.1) into a 50 mL volumetric flask with a small amount of hot water, shake well, and cool to room temperature. Add

2.0 mL of ascorbic acid solution (4.2.3) and

10.0 mL of diantipyrin methane solution (4.2.4) were diluted with water to the mark, shaken well, and left to stand. 15 minutes.

4.5.4.3 Measurement. Transfer a portion of the test solution (4.5.4.2) into a 1 cm or 5 cm absorption cell, and measure it at the wavelength (4.3.2) of a spectrophotometer. At 390 nm, using water as a reference, the absorbance was measured. The absorbance of the blank test solution (4.5.3) was then subtracted from the measured absorbance, and the result was obtained from the corresponding working... The mass of titanium dioxide was determined by plotting the curve.

4.5.5 Drawing the working curve

4.5.5.1 Transfer 0 mL,

10.0 mL of titanium dioxide standard solution (4.2.6) into a container. In a 50 mL volumetric flask, add 8 mL of hydrochloric acid (4.2.2) or 10 mL of sulfuric acid solution (4.2.1),

2.0 mL of ascorbic acid solution (4.2.3), and... Dilute

10.0 mL of diantipyrin methane solution (4.2.4) with water to the mark, shake well, and let stand for 15 min.

4.5.5.2 Transfer the series of standard solutions (4.5.5.1) into a 1 cm or 5 cm absorption cell and measure them at a wavelength of 390 nm using a spectrophotometer (4.3.2). At a concentration of 10... Plot the working curve with absorbance as the ordinate.

4.6 Experimental Data Processing The content of titanium dioxide (wTiO2) is expressed as a mass fraction and calculated according to formula (1).

4.7 Precision

4.7.1 Repeatability Limit (r) The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 3, are these two measured values. The absolute difference should not exceed the repeatability limit (r), and the number of cases exceeding the repeatability limit (r) should not exceed 5%. The repeatability limit (r) is calculated using linear data from Table 3. It can be obtained by interpolation or extension.

4.7.2 Reproducibility Limit (R) The measured values of two independent test results obtained under reproducibility conditions, within the range of the average values given in Table 4, are these two measured values. The absolute difference should not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) should not exceed 5%. The reproducibility limit (R) is determined according to the data in Table 4. Obtained by linear interpolation or extrapolation.

5.2 Reagents Warning

---The sodium azide crystals used in this experiment are toxic and will explode when heated, exposed to open flames, or subjected to friction, vibration, or impact. If an explosion occurs, personnel must take protective measures to avoid direct contact with the human body or to prevent an explosion. Unless otherwise specified, only reagents confirmed to be of superior purity and Class II water conforming to GB/T 6682 shall be used in the analysis.

5.2.1 Boric acid.

5.2.2 Anhydrous sodium carbonate.

5.2.3 Sulfuric acid (

2.5 mol/L). Dissolve 136 mL of sulfuric acid (rho =

1.84 g/cm3) in 846 mL of water and mix well.

5.2.4 Phosphoric acid (1 3).

5.2.5 Potassium permanganate solution (3g/L).

5.2.6 Sodium azide solution (

5.2.7 Diphenylcarbazide solution (4 g/L). Weigh 8 g of phthalic anhydride and add it to 180 mL of anhydrous ethanol. Place the solution in a hot water bath and add... Dissolve by heating. After cooling, add

0.8 g of diphenylcarbazide, stir, and after dissolving, dilute with anhydrous ethanol to.200 mL (if there are insoluble substances, [the solution should be adjusted]). (Filter), mix well, and store in a brown bottle. If the solution is brownish-yellow or reddish-brown, prepare another solution.

5.2.8 Chromium trioxide standard stock solution. Weigh 0.1936 g of potassium dichromate (pre-dried in an oven at 120°C±3°C (5.3.4)). [After 2 hours, cool to room temperature in a desiccator (5.3.5)] Dissolve in water in a 150 mL beaker, transfer to a 1000 mL volumetric flask, and add... Dilute 20 mL of sulfuric acid (5.2.3) to the mark with water and mix well. 1 mL of this solution contains 0.1000 mg of chromium trioxide.

5.2.9 Chromium Trioxide Standard Solution A. Transfer

50.00 mL of chromium trioxide standard stock solution (5.2.8) into a 500 mL volumetric flask. Dilute with water to the mark and mix well. 1 mL of this solution contains 10 µg of chromium trioxide. Prepare fresh before use.

5.2.10 Chromium Trioxide Standard Solution B. Transfer

25.00 mL of chromium trioxide standard stock solution (5.2.8) into a 1000 mL volumetric flask. Dilute with water to the mark and mix well. 1 mL of this solution contains 2.5 µg of chromium trioxide; prepare fresh before use.

5.3 Instruments and Equipment

5.3.1 Spectrophotometer with absorption cells of 1 cm and 3 cm.

5.3.2 Platinum crucible. 30mL~50mL, with lid.

5.3.3 Muffle furnace. The temperature can be controlled at 1000°C±20°C.

5.3.4 Oven. The temperature can be controlled at 300°C±10°C.

5.3.5 Dryer. Use activated alumina as a desiccant, and activate it at 300°C before each use.

5.4 Test Procedure

5.4.1 Sample Weigh the sample (4.4) according to Table 5, accurate to 0.0001g.

5.4.2 Parallel Tests Perform two parallel experiments and take the average value.

5.4.3 Blank Test A blank test was performed along with the sample.

5.4.4 Measurement

5.4.4.1 Place the sample (5.4.1) in a platinum crucible (5.3.2), add flux according to Table 5, stir well with a platinum spoon, cover the crucible, and place it in a low-temperature environment. In a muffle furnace (5.3.3) at 700°C, the temperature was raised to 1000°C and melted for 20 minutes, then removed and slightly cooled. The blank sample was directly melted at 1000°C along with the sample. Melt for 2-3 minutes, then remove and let cool slightly.

Note. If 1g of sample is melted in a 30mL crucible, a heating time of 50min~60min is appropriate when the melting temperature is increased from 700°C to 1000°C.

5.4.4.2 Add boiling water to the platinum crucible and heat near the boiling point to dissolve the melt. Transfer the solution to a container pre-filled with sulfuric acid (5.2.3) as per Table 5. In a 100mL beaker containing 2mL of phosphoric acid (5.2.4), rinse the platinum crucible 2-3 times with hot water, adding the washings to the beaker, and stir until the melt is completely dissolved. To dissolve the partially dissolved sulfuric acid, add 1 mL of sulfuric acid (5.2.3) to the platinum crucible, and heat water to approximately three-quarters of the crucible's volume, stirring until well combined. Heat to near... Boil and maintain for 15 minutes. Combine the solution in a beaker. Wash the platinum crucible and lid with hot water. Cover the beaker with a watch glass and heat on a hot plate until a precipitate forms. Dissolved completely.

5.4.4.3 Add potassium permanganate solution (5.2.5) dropwise until the solution turns red, then add 4 drops in excess. Heat to a gentle boil and maintain for 30 minutes. If the solution turns red during heating... If the color lightens, add potassium permanganate solution (5.2.5), keeping the solution volume at approximately 25 mL. Add sodium azide solution (5.2.6) dropwise until the red color fades. Add one drop at a time, heating for 1-2 minutes before adding the next drop, and add an excess of one drop. Continue heating for 2 minutes, remove from heat and let cool slightly, then transfer the solution to... In a 50mL volumetric flask, control the volume to approximately 45mL and cool to room temperature. If the room temperature is high, the colorimetric time needs to be carefully controlled, or the flask can be cooled to room temperature with running water. Color develops after 20°C~25°C.

Note. Temperature has a significant impact on the stability of the complex. It is stable for about 2 hours at 20°C, about 40 minutes at 25°C, and only about 10 minutes at 35°C.

5.4.4.4 Add 2 mL of diphenylcarbazide solution (5.2.7), dilute with water to the mark, mix well, and let stand for 3 min.

5.4.4.5 Transfer a portion of the test solution (5.4.4.4) to an appropriate absorption cell according to Table 5, and measure it at a wavelength of 550 nm using a spectrophotometer (5.3.1). At the reference point, using water, the absorbance was measured. The absorbance of the blank test solution (5.4.3) was then subtracted from the measured absorbance, and the result was obtained from the corresponding working curve. The mass of chromium trioxide was found.

5.4.5 Plotting the Working Curve

5.4.5.1 Add 0 mL,

5.00 mL to a set of 50 mL volumetric flasks respectively. Add

7.00 mL of chromium trioxide standard solution A (5.2.9), 2 mL of sulfuric acid (5.2.3), and 2 mL of phosphoric acid (5.2.4), then dilute with water. Add 2 mL of diphenylcarbazide solution (5.2.7) to approximately 45 mL, dilute with water to the mark, mix well, and let stand for 3 min.

5.4.5.2 Transfer a portion of the series of standard solutions (5.4.5.1) into a 1 cm absorption cell and measure them at a wavelength of 550 nm using a spectrophotometer (5.3.1). At a concentration of chromium trioxide, the absorbance was measured using water as a reference. The absorbance was then subtracted from the absorbance of the "zero" concentration solution, and the result was plotted against the mass of chromium trioxide. Plot the working curve with absorbance as the ordinate.

5.4.5.3 Add 0 mL,

5.00 mL to a set of 50 mL volumetric flasks respectively. Add

9.00 mL of chromium trioxide standard solution B (5.2.10), 2 mL of sulfuric acid (5.2.3), and 2 mL of phosphoric acid (5.2.4), and dilute with water. Dilute to approximately 45 mL, add 2 mL of diphenylcarbazide solution (5.2.7), dilute with water to the mark, mix well, and let stand for 3 min.

5.4.5.4 Transfer a portion of the series of standard solutions (5.4.5.3) into a 3 cm absorption cell and measure them at a wavelength of 550 nm using a spectrophotometer (5.3.1). At a concentration of chromium trioxide, the absorbance was measured using water as a reference. The absorbance was then subtracted from the absorbance of the "zero" concentration solution, and the result was plotted against the mass of chromium trioxide. Plot the working curve with absorbance as the ordinate.

5.5 Experimental Data Processing The chromium trioxide content (wCr2O3) is calculated as a mass fraction according to formula (2).

5.6 Precision

5.6.1 Repeatability Limit (r) The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given below, represent the two test results. The absolute difference does not exceed the repeatability limit (r), and the number of cases exceeding the repeatability limit (r) does not exceed 5%. The repeatability limit (r) is determined by linearity according to the data in Table 6. Obtained by the intrinsic method or the extrapolation method.

5.6.2 Permissible Difference The difference between analytical results from different laboratories should not exceed the allowable difference listed in Table 7.

6.2 Reagents Warning

---The chloroform used in this document can cause harm to the human body if inhaled or absorbed through the skin. It will react with oxygen in the air when exposed to light. The process involves the release of toxic gases, so protective equipment must be worn during the experiment, and the experiment must be conducted under well-ventilated conditions. Unless otherwise specified, only reagents confirmed to be of superior purity and Class II water conforming to GB/T 6682 shall be used in the analysis.

6.2.1 Anhydrous sodium carbonate.

6.2.2 Boric acid.

6.2.3 Chloroform, store protected from light.

6.2.4 Hydrochloric acid (1 1).

6.2.5 Sodium hydroxide solution (200 g/L).

6.2.6 Hydroxylamine hydrochloride solution (100g/L). Prepare fresh before use.

6.2.7 Ammonium citrate solution (500 g/L).

6.2.8 Neo-Copperamine-Ethanol Solution (

0.10 g of 2,9-dimethyl-1,10-phenanthroline and dissolve it in anhydrous ethanol. Then, use anhydrous ethanol... Dilute the alcohol to 100 mL and let stand for at least 12 hours.

6.2.9 Standard stock solution of copper oxide. Weigh 0.0799 g of metallic copper powder (wCu>=99.9%) [pre-dry in a desiccator (6.3.5)]. [24h] In a beaker, add

10.00 mL of water and

10.00 mL of nitric acid (1.1), cover with a watch glass, and after complete dissolution, heat to boiling to remove nitrogen. The oxide was cooled and transferred to a 1000 mL volumetric flask, diluted to the mark with water, and mixed well. 1 mL of this solution contains

0.1 mg of copper oxide.

6.2.10 Copper oxide standard solution. Transfer

10.00 mL of copper oxide standard stock solution (6.2.9) to a 100 mL volumetric flask and dilute with water. Fill to the mark and mix well. This solution contains

0.01 mg of copper oxide per mL; prepare fresh before use.

6.2.11 Copper oxide standard solution. Transfer

20.00 mL of copper oxide standard solution (6.2.10) into a 50 mL volumetric flask and dilute with water to the mark. Mix thoroughly. This solution contains 4 µg of copper oxide per mL; prepare fresh before use.

6.3 Instruments and Equipment

6.3.1 Spectrophotometer with absorption cells of 1 cm and 2 cm.

6.3.2 Platinum crucible. 30mL~50mL, with lid.

6.3.3 Muffle furnace. The temperature can be controlled at 1000°C±20°C.

6.3.4 Oven. The temperature can be controlled at 300°C±10°C.

6.3.5 Dryer. Use activated alumina as a desiccant, and activate it at 300°C before each use.

6.4 Test Procedure

6.4.1 Sample Weigh the sample (4.4) according to Table 8, accurate to 0.0001g.

6.4.2 Parallel Tests Perform two parallel experiments and take the average value.

6.4.3 Blank Test A blank test was performed along with the sample.

6.4.4 Measurement

6.4.4.1 Place the sample (6.4.1) in a platinum crucible (6.3.2), add flux according to Table 8, stir well with a platinum spoon, cover with the platinum crucible lid, and place at a temperature... In a muffle furnace (6.3.3) below 700°C, the temperature is slowly increased to 1000°C±20°C and melted for 20 minutes. The blank sample is directly melted at 1000°C± Melt at 20°C for 2-3 minutes. Remove and let cool slightly. Add boiling water to the crucible and heat on a hot plate until the molten metal is completely melted. Let it cool slightly. Transfer it to a 100 mL beaker containing hydrochloric acid (6.2.4) pre-added according to Table

8.Wash the crucible with hot water and add the washing liquid to the beaker. Stir and heat to dissolve the precipitate, remove and cool to room temperature.

6.4.4.2 Add

10.0 mL of ammonium citrate solution (6.2.7), mix well, add

5.0 mL of hydroxylamine hydrochloride solution (6.2.6), mix well, then add... Add

5.0 mL of neoquinazon-ethanol solution (6.2.8), mix well, and adjust the solution with sodium hydroxide solution (6.2.5) until the Congo red test paper just turns red. Transfer the solution to... Pour into a 125 mL separatory funnel, rinse the beaker with water, and add the washings to the separatory funnel to make the solution volume approximately 70 mL. Shake well. Add

10.00 mL of chloroform (6.2.3), shake and extract for 1 min, then allow to stand for separation.

6.4.4.3 Wipe the funnel neck dry with filter paper, and place a portion of the solution (6.4.4.2) into the absorption cell according to Table

8.Analyze the solution at wavelength (6.3.1) on a spectrophotometer. The absorbance was measured at 460 nm using chloroform (6.2.3) as a reference. The absorbance of the blank test solution (6.4.3) was then subtracted from the measured absorbance. Then, the corresponding copper oxide mass was obtained from the working curve.

6.4.5 Plotting the Working Curve

6.4.5.1 When the copper oxide content is not greater than 0.0020%. Add 25 mL of water and

3.0 mL of [unspecified substance] to a set of 125 mL separatory funnels respectively. Hydrochloric acid (6.2.4), then add 0 mL,

0.25 mL,

0.50 mL,

5.00 mL of oxidizing agent respectively. Prepare the copper standard solution (6.2.11), shake well, and proceed as per 6.4.4.2.Wipe the funnel neck dry with filter paper.

6.4.5.2 Transfer a portion of the series of standard solutions (6.4.5.1) into a 2 cm absorption cell, and precipitate them at a spectrophotometer wavelength of 460 nm using chloroform. Using (6.2.3) as a reference, its absorbance was measured. The absorbance of the measured solution was subtracted from the absorbance of the zero-concentration solution, and the result was plotted with the mass of copper oxide on the x-axis. Plot the working curve with absorbance as the ordinate.

6.4.5.3 When the copper oxide content is greater than or equal to 0.0020%. Add 25 mL of water and

3.0 mL of [unspecified substance] to a set of 125 mL separatory funnels respectively. Hydrochloric acid (6.2.4), then add 0 mL,

7.00 mL of oxidizing agent respectively. Prepare the copper standard solution (6.2.10), shake well, and proceed as per 6.4.4.2.Wipe the funnel neck dry with filter paper.

6.4.5.4 Transfer a portion of the series of standard solutions (6.4.5.3) into a 1 cm absorption cell, and analyze it at a wavelength of 460 nm using a spectrophotometer (6.3.1). Using chloroform (6.2.3) as a reference, its absorbance was determined. The absorbance was then subtracted from the absorbance of the zero-concentration solution, with the mass of copper oxide as the reference value. Plot the working curve with absorbance as the ordinate and the horizontal axis as the horizontal axis.

6.6 Precision

6.6.1 Repeatability Limit (r) The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given below, represent the two test results. The absolute difference does not exceed the repeatability limit (r), and the number of cases exceeding the repeatability limit (r) does not exceed 5%. The repeatability limit (r) is determined by linearity according to the data in Table 9. Obtained by the intrinsic method or the extrapolation method.

7.2.4 Lanthanum solution (

0.095 g of lanthanum oxide [pre-calculated at 1000 °C for 2 h, then cooled to room temperature in a desiccator (7.3.4)]. Place the solution in a beaker, add 3 mL of hydrochloric acid (7.2.1), heat gently to dissolve, then add water to 50 mL and mix well.

7.2.5 Colorimetric Solution. Weigh

0.200 g of alizarin complexing indicator into a 150 mL dry beaker, add 2 mL of ammonia water (rho =

0.90 g/mL), and stir. After dissolving, add water to 100 mL, add 25 g of sodium acetate trihydrate (CH3COONa·3H2O), stir until dissolved, and then transfer to... In a 1000mL volumetric flask, add 30mL of glacial acetic acid (rho=1.05g/mL), and slowly add 500mL of acetone (rho=) while shaking.

0.79 g/mL) and 50 mL of lanthanum solution (7.2.4) were diluted to the mark with water, mixed well, and stored in a brown bottle. This solution should be left to stand for 8 hours after preparation. It can be used afterward. Before use, filter with medium-speed quantitative filter paper. It can be stored in a light-proof and airtight container below 25°C for at least 21 days.

7.2.6 Fluorine Standard Stock Solution. Weigh 0.2210 g of high-purity sodium fluoride (pre-placed in a platinum crucible, ignited at 600°C for 2 h, and then placed in a desiccator). (Cooled to room temperature) Place in a 150 mL beaker, dissolve in water, transfer to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. Storage In a polyethylene bottle. This solution contains

0.1 mg of fluoride per mL. Alternatively, use a commercially available, certified solution.

7.2.7 Fluorine Standard Solution. Transfer

50.00 mL of the fluorine standard stock solution (7.2.6) to a 1000 mL volumetric flask, dilute to the mark with water, and mix. Uniform. 1 mL of this solution contains 5 µg of fluorine.

7.3 Instruments and Equipment

7.3.1 Spectrophotometer, absorption cell 1 cm.

7.3.2 Schematic diagrams of the distillation-absorption apparatus are shown in Figures A.2 to A.4.New quartz tubes can be treated by washing or ignition. Old quartz tubes should be treated using... Treatment by incineration.

7.3.3 Oven. The temperature can be controlled at 300°C±10°C.

7.3.4 Dryer. Use activated alumina as a desiccant, and activate it at 300°C before each use.