GB/T 13748.4-2026Methods for chemical analysis of magnesium and magnesium alloys - Part 4: Determination of manganese and zirconium content - Spectrophotometry (English PDF)

6.1 Periodate Spectrophotometry (I)

6.1.1 Method Overview The sample was dissolved in sulfuric acid, and in the presence of fluoroboric acid and nitric acid, divalent manganese ions were oxidized to heptavalent manganese ions using potassium periodate. The oxidized manganese was then analyzed by spectrophotometry. The absorbance was measured at a wavelength of 525 nm using a thermometer. The mass of manganese was determined from the working curve, and the mass fraction of manganese was calculated.

6.1.2 Reagents Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

6.1.2.1 Potassium periodate.

6.1.2.2 Nitric acid (rho=1.42g/mL).

6.1.2.3 Sulfuric acid (1 3).

6.1.2.4 Fluoroboric acid (1 99).

6.1.2.5 Reducing agent removal water. Take 1L of water, add 10mL of sulfuric acid (6.1.2.3) and a small amount of potassium periodate (6.1.2.1), boil for about 10 minutes, and cool. Use it as a backup.

6.1.3 Test Procedure

6.1.3.1 Sample Weigh the sample according to Table 2 (Chapter 5), accurate to 0.0001g, and record it as m0.

6.1.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

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

6.1.3.4 Measurement 6.1.3.4.1 Place the sample in a 250mL beaker, cover with a watch glass, and slowly add sulfuric acid according to Table 1 (6.1.2.3) until the sample is completely dissolved. Then, add 20 mL of nitric acid (6.1.2.2) and 5 mL of fluoroboric acid (6.1.2.4), and dilute with water to approximately 60 mL. If the mass fraction of manganese is greater than... 0.50%, transfer the test solution to a 100 mL volumetric flask (V0), dilute to the mark with water, and mix well. Transfer

10.00 mL of the test solution (V1) to... In a 250mL beaker, add 15mL of sulfuric acid (6.1.2.3), 20mL of nitric acid (6.1.2.2), and 5mL of fluoroboric acid (6.1.2.4), and dilute with water to approximately [amount missing]. 60mL. 6.1.3.4.2 Boil the test solution for 1 to 2 minutes, let it cool slightly, add

0.5 g of potassium periodate (6.1.2.1), continue boiling for 3 minutes, and keep warm. After 10 minutes, cool to room temperature, transfer to a 100 mL volumetric flask, dilute to the mark with water (6.1.2.5) to remove the reducing agent, and mix well. 6.1.3.4.3 Transfer a portion of the test solution into a 1cm cuvette, add sodium nitrite solution (6.1.2.6) to the remaining test solution, and shake until the purple color just turns purple. After fading, transfer a portion of the solution to another 1cm cuvette as a reference, and measure it at a wavelength of 525nm using a spectrophotometer (Chapter 4). Measure its absorbance. 6.1.3.4.4 Subtract the absorbance of the blank test solution from the absorbance of the measured test solution, and find the mass of manganese (mMn) from the working curve.

6.1.3.5 Drawing the working curve 6.1.3.5.1 Transfer 0 mL,

15.00 mL of manganese standard solution respectively. (6.1.2.8) Place the mixture in a set of 250mL beakers, and add 15mL of sulfuric acid (6.1.2.3), 20mL of nitric acid (6.1.2.2), and 5mL of fluoroboric acid respectively. (6.1.2.4) Dilute with water to about 60 mL and proceed according to steps 6.1.3.4.2 to 6.1.3.4.3. 6.1.3.5.2 Using the "zero" concentration solution in the standard solution series of the working curve as a reference, with the mass of manganese as the abscissa and the corresponding absorbance as the ordinate. Use coordinates to plot the working curve. The linear correlation coefficient of the working curve should be no less than 0.999.

6.1.5 Precision

6.1.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 3, represent the values of 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 based on the data in Table 3. Obtained by interpolation or extrapolation.

6.1.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of average values given in Table 4, represent the values of the two test results. The absolute difference does not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) does not exceed 5%. The reproducibility limit (R) is calculated using linearity based on the data in Table 4. Obtained by interpolation or extrapolation.

6.2 Periodate spectrophotometry (II)

6.2.1 Method Overview The sample was dissolved in sulfuric acid, oxidized with nitric acid, and then, in the presence of phosphoric acid, dimethylmanganese ions were oxidized to heptavalent manganese ions with potassium periodate. The results were then analyzed by spectrophotometry. The absorbance was measured at a wavelength of 525 nm using a thermometer. The mass of manganese was determined from the working curve, and the mass fraction of manganese was calculated.

6.2.2 Reagents or materials Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

6.2.2.1 Potassium periodate.

6.2.2.2 Nitric acid (rho=1.42g/mL).

6.2.2.3 Phosphoric acid (rho=1.71g/mL).

6.2.2.4 Hydrofluoric acid (rho=1.14g/mL).

6.2.2.5 Sulfuric acid (1 3).

6.2.2.6 Sodium nitrite solution (20g/L), prepared fresh before use.

6.2.2.7 Reducing agent removal water. Take 1L of water, add 10mL of sulfuric acid (6.2.2.5) and a small amount of potassium periodate (6.2.2.1), boil for about 10 minutes, and cool. Use it as a backup.

6.2.2.8 Manganese standard stock solution (1 mg/mL). Prepared in any of the following ways, or using a certified standard solution.

---Weigh 1.0000g of electrolytic manganese [wMn>=99.9%], pre-wash with sulfuric acid (6.2.2.5) to remove surface oxides, then wash with water and... [Wash with ethanol and dry, then cool] Place in a 400mL beaker, add 40mL of sulfuric acid (6.2.2.5), heat to dissolve, and add approximately... Boil 80 mL of water for 5 minutes, cool to room temperature, transfer to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. This solution... 1 mL contains 1 mg of manganese. Weigh 2.8770 g of potassium permanganate (primary standard) into a 400 mL beaker and dissolve it in approximately.200 mL of water. Add 40 mL of... Sulfuric acid (6.2.2.5), appropriate amount of sodium sulfite or hydrogen peroxide (rho=1.10g/mL), boil, cool, and transfer to a 1000mL volumetric flask. Dilute with water to the mark and mix well. 1 mL of this solution contains 1 mg of manganese.

6.2.2.9 Manganese Standard Solution (100 µg/mL). Transfer

10.00 mL of manganese standard stock solution (6.2.2.8) to a 100 mL volumetric flask, and add water. Dilute to the mark and mix well. 1 mL of this solution contains 100 µg of manganese.

6.2.3 Test Procedure

6.2.3.1 Sample Weigh the sample according to Table 5 (Chapter 5), accurate to 0.0001g, and record it as m1.

6.2.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

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

6.2.3.4 Measurement 6.2.3.4.1 Place the sample in a 250mL beaker, cover with a watch glass, add 10mL of water, and slowly add sulfuric acid according to Table 4 (6.2.2.5). After the sample is completely dissolved, add nitric acid (6.2.2.2) and 2-3 drops of hydrofluoric acid (6.2.2.4) according to Table 4, boil for 5 minutes, remove from heat, and cool. If If the manganese mass fraction is greater than 0.50%, transfer the test solution to a 100 mL volumetric flask (V2), dilute to the mark with water, and mix well. Transfer

10.00 mL of the solution. In a 250 mL beaker, add 15 mL of sulfuric acid (6.2.2.5) and 20 mL of nitric acid (6.2.2.2). 6.2.3.4.2 Dilute the test solution with water to approximately 60 mL, add 5 mL of phosphoric acid (6.2.2.3), heat to boiling, and add

0.5 g of potassium periodate. (6.2.2.1) Boil for 3 minutes, keep warm at near boiling for 10 minutes, cool, transfer to a 100 mL volumetric flask, and dilute with water (6.2.2.7) to remove the reducing agent. Add water to the mark and mix well. 6.2.3.4.3 Transfer a portion of the solution into a 1cm cuvette. Add sodium nitrite solution (6.2.2.6) to the remaining solution and shake until the purple color just begins to appear. After fading, transfer a portion of the solution to another 1cm cuvette as a reference, and measure its absorbance at a wavelength of 525nm using a spectrophotometer (4). Luminosity. 6.2.3.4.4 Subtract the absorbance of the blank test solution that was used as a sample from the absorbance of the measured test solution, and find the mass of manganese (mMn) from the working curve.

6.2.3.5 Plotting the Working Curve 6.2.3.5.1 Transfer 0 mL,

15.00 mL of manganese standard solution, respectively. (6.2.2.9) Place in a set of 250mL beakers, add 15mL of sulfuric acid (6.2.2.5) and 20mL of nitric acid (6.2.2.2), and proceed according to 6.2.3.4.2~ Proceed with steps 6.2.3.4.3. 6.2.3.5.2 Using the "zero" concentration solution in the standard solution series of the working curve as a reference, with the mass of manganese as the abscissa and the corresponding absorbance as the ordinate. Use coordinates to plot the working curve. The linear correlation coefficient of the working curve should be no less than 0.999.

6.2.5 Precision

6.2.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 6, represent the values of 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 based on the data in Table 6. Obtained by interpolation or extrapolation.

6.2.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of average values given in Table 7, represent the values of the two test results. The absolute difference does not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) does not exceed 5%. The reproducibility limit (R) is calculated using linearity based on the data in Table 7. Obtained by interpolation or extrapolation.

6.3 Periodate Spectrophotometry (III)

6.3.1 Method Overview The sample was dissolved in sulfuric acid, oxidized with nitric acid, and then, in the presence of phosphoric acid, oxidized divalent manganese ions to heptavalent manganese ions with potassium periodate. The results were then analyzed by spectrophotometry. The absorbance was measured at a wavelength of 525 nm using a thermometer. The mass of manganese was then determined from the working curve, and the mass fraction of manganese was calculated.

6.3.2 Reagents or materials Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

6.3.2.1 Nitric acid (rho=1.40g/mL).

6.3.2.2 Phosphoric acid (rho=1.71g/mL).

6.3.2.3 Sulfuric acid (1 3).

6.3.2.4 Potassium periodate solution (50 g/L). Weigh 25 g of potassium periodate into a 500 mL beaker, add 400 mL of water, and heat to dissolve. Then, add 100 mL of nitric acid (6.3.2.1) and mix well.

6.3.2.5 Sodium nitrite solution (5g/L), prepared fresh before use.

6.3.2.6 Reducing agent removal water. Take 1000mL of water, add 10mL of sulfuric acid (6.3.2.3) and a small amount of potassium periodate, boil for 10 minutes, and then cool. spare.

6.3.2.7 Manganese standard stock solution (1 mg/mL). Prepared in any of the following ways, or using a certified standard solution.

---Weigh 1.0000g of electrolytic manganese [wMn>=99.9%], pre-wash with sulfuric acid (6.3.2.3) to remove surface oxides, then wash with water and... [Wash with aqueous ethanol (rho=0.79g/mL), dry and cool] Place in a 400mL beaker, add 40mL of sulfuric acid (6.3.2.3), and heat. Dissolve, add about 80 mL of water, boil for 5 minutes, cool to room temperature, transfer to a 1000 mL volumetric flask, and dilute with water to the mark. Mix thoroughly. 1 mL of this solution contains 1 mg of manganese. Weigh 2.8770 g of potassium permanganate (primary standard) into a 400 mL beaker and dissolve it in approximately.200 mL of water. Add 40 mL of... Sulfuric acid (6.3.2.3), appropriate amount of sodium sulfite or hydrogen peroxide (rho=1.10g/mL), boil, cool, and transfer to a 1000mL volumetric flask. Dilute with water to the mark and mix well. 1 mL of this solution contains 1 mg of manganese.

6.3.2.8 Manganese Standard Solution (20 µg/mL). Transfer

10.00 mL of manganese standard stock solution (6.3.2.7) to a 500 mL volumetric flask, and add water. Dilute to the mark and mix well. 1 mL of this solution contains 20 µg of manganese.

6.3.3 Test Procedure

6.3.3.1 Sample Weigh the sample according to Table 8 (Chapter 5), accurate to 0.0001g, and record it as m2.

6.3.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

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

6.3.3.4 Measurement

6.3.3.5 Plotting the Working Curve 6.3.3.5.1 Transfer 0 mL,

0.50 mL,

5.00 mL of manganese standard solution respectively. (6.3.2.8) In a 250 mL beaker, add 10 mL of sulfuric acid (6.3.2.3), 5 mL of nitric acid (6.3.2.1), and 1 mL of phosphoric acid (6.3.2.2), respectively, and mix. Mix well and dilute with water to a volume of approximately 50 mL. Proceed according to steps 6.3.3.4.2 to 6.3.3.4.3. 6.3.3.5.2 Using the "zero" concentration solution in the standard solution series of the working curve as a reference, with the mass of manganese as the abscissa and the corresponding absorbance as the ordinate. Use coordinates to plot the working curve. The linear correlation coefficient of the working curve should be no less than 0.999.

6.3.5 Precision

6.3.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 9, 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 based on the data in Table 9. Obtained by interpolation or extrapolation.

7.1 Xylenol Orange Spectrophotometric Method

7.1.1 Method Overview The sample was decomposed with hydrochloric acid and hydrofluoric acid, and perchloric acid was added to remove fluoride ions. The acidity was adjusted with perchloric acid, and xylenol orange was added to react with zirconium to form... The red complex was analyzed, and its absorbance was measured at a spectrophotometer at a wavelength of 535 nm. The mass of zirconium was determined from the working curve, and the zirconium content was calculated. Quality score.

7.1.2 Reagents or materials Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

7.1.2.1 Hydrofluoric acid (rho=1.14g/mL).

7.1.2.2 Perchloric acid (rho=1.69g/mL).

7.1.2.3 Perchloric acid [c(HClO4)=6.5mol/L]. Transfer 275mL of perchloric acid (7.1.2.2), dilute with water to 500mL, and mix well.

7.1.2.4 Hydrochloric acid (1 1).

7.1.2.5 Washing solution. Take 1000mL of water, add 20mL of hydrochloric acid (rho=1.19g/mL) and 50mL of mandelic acid solution (150g/L), and heat. Dissolve completely. Filter if necessary.

7.1.3 Test Procedure

7.1.3.1 Sample Weigh the sample according to Table 11 (Chapter 5), accurate to 0.0001g, and record it as m3.

7.2 Alizarin sulfonate spectrophotometry (I)

7.2.1 Method Overview The sample was dissolved in hydrochloric acid, filtered, and the acid-insoluble zirconium was dissolved in hydrofluoric acid and perchloric acid. Upon heating in hydrochloric acid, zirconium reacts with alizarin sulfonate to form... The absorbance of the complex was measured at a wavelength of 525 nm using a spectrophotometer. The mass of zirconium was determined from the working curve, and the acid insolubility was calculated. Mass fraction of zirconium.

7.2.2 Reagents or materials Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

7.2.2.1 Hydrochloric acid (rho=1.19g/mL).

7.2.2.2 Hydrofluoric acid (rho=1.14g/mL).

7.2.2.3 Perchloric acid (rho=1.69g/mL).

7.2.2.4 Alizarin sulfonate sodium solution (

1.5 g of alizarin sulfonate sodium (C14H7NaO7S) and dissolve it in 300 mL of warm water. Filter, cool, dilute with water to 1000 mL, and mix well.

7.2.2.5 Magnesium chloride solution (420 g/L). Weigh 42 g of magnesium chloride hexahydrate (MgCl2·6H2O), dissolve it in water, and dilute with water to a final concentration of 420 g/L. Mix 100 mL thoroughly. 1 mL of this solution contains 50 mg of magnesium.

7.2.2.7 Zirconium Standard Solution (100 µg/mL). Transfer

50.00 mL of zirconium standard stock solution (7.2.2.6) to a 500 mL volumetric flask, add... Dilute 80 mL of hydrochloric acid (7.2.2.1) to the mark with water and mix well. 1 mL of this solution contains 100 µg of zirconium. Prepare fresh before use.

7.2.3 Test Procedure

7.2.3.1 Sample Weigh the sample according to Table 14 (Chapter 5), accurate to 0.0001g, and record it as m4.

7.2.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

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

7.2.3.4 Measurement 7.2.3.4.1 Place the sample in a 600 mL beaker, cover with a watch glass, and add water and hydrochloric acid in portions according to Table 13 (7.2.2.1). Wait for the reaction to stop. Then, heat slowly until the sample is completely dissolved, and boil for 5 minutes. Filter with medium-speed filter paper and wash the residue with hot water. 7.2.3.4.2 Transfer the residue and filter paper to a 100 mL platinum dish, dry, ashed at 700 °C, cool, and add 5 mL of water and 1 mL of hydrofluoric acid. (7.2.2.2) Add 2 mL of perchloric acid (7.2.2.3), heat to evaporate until the solution is nearly dry, wash the dish walls with a small amount of water, and then add 2 mL of perchloric acid. (7.2.2.3) Evaporate until the solution is nearly dry. Add a small amount of water, heat to dissolve completely, and then cool. 7.2.3.4.3 When the magnesium alloy does not contain silver, transfer the test solution into a 100mL volumetric flask (V6), rinse the platinum dish with water, dilute to the mark with water, and mix. When the magnesium alloy contains silver, transfer the test solution to a 250 mL beaker, wash the platinum dish with water, add 15 mL of hydrochloric acid (7.2.2.1), and boil. After 5 minutes, add 50 mL of water, boil, and cool to room temperature. Filter through slow-speed filter paper containing a small amount of fiber pulp, and wash away the precipitate and filter paper with water. Collect the filtrate and washings in a 100 mL volumetric flask (V6), dilute with water to the mark, and mix well. 7.2.3.4.4 Transfer the test solution (V7) according to Table 15 into a 100mL dry conical flask, and add water to a volume of 10mL. Add hydrochloric acid according to Table 15. (7.2.2.1) Prepare

10.0 mL of sodium alizarin sulfonate solution (7.2.2.4). Place the conical flask in a boiling water bath for 3 minutes, then remove and immediately cool to room temperature. Add

2.0 mL of hydrochloric acid (7.2.2.1) to the warm water, transfer the solution to a 100 mL volumetric flask, dilute with water to the mark, and mix well. 7.2.3.4.5 Transfer a portion of the solution into a 1cm cuvette, using the blank test solution along with the sample as a reference, and analyze it within 1 hour using a spectrophotometer. The absorbance was measured at a wavelength of 525 nm, and the mass of zirconium (mZr) was obtained from the working curve.

7.2.3.5 Plotting the Working Curve 7.2.3.5.1 Transfer 0 mL,

8.00 mL of zirconium standard solution (7.2.2.7) to a container, respectively. In each of the 100mL dry conical flasks, add 2mL of magnesium chloride solution (7.2.2.5), then add water to make the solution volume 10.0mL.

2.5 mL of hydrochloric acid (7.2.2.1) and

10.0 mL of sodium alizarin sulfonate solution (7.2.2.4) were added. The conical flask was placed in a boiling water bath and kept for 3 minutes. Immediately cool to room temperature, add

2.0 mL of hydrochloric acid (7.2.2.1), transfer the solution to a 100 mL volumetric flask, and dilute to the mark with water. Mix well. 7.2.3.5.2 Transfer a portion of the solution into a 1cm cuvette, using the "zero" concentration solution from the standard solution series of the working curve as a reference, and incubate for 1 hour. The absorbance of zirconium was measured at a wavelength of 525 nm using a spectrophotometer (Chapter 4). The mass of zirconium was plotted on the x-axis, and the corresponding absorbance on the y-axis. Plot the working curve. The linear correlation coefficient of the working curve should not be less than 0.999.

7.2.5 Precision

7.2.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 16, 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 defined using linear data from Table 16. It can be obtained by interpolation or extension.

7.2.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of the average values given in Table 17, represent the two test results. The absolute difference does not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) does not exceed 5%. The reproducibility limit (R) is determined according to the data in Table 17. Obtained by linear interpolation or extrapolation.

7.3 Alizarin sulfonate spectrophotometry (II)

7.3.1 Method Overview The sample was dissolved in hydrochloric acid, filtered, and heated in hydrochloric acid. Zirconium reacted with alizarin sulfonate to form a complex, which was then analyzed at a spectrophotometer wavelength of 525 nm. Measure its absorbance, find the mass of zirconium according to the working curve, and calculate the mass fraction of acid-soluble zirconium.

7.3.2 Reagents or materials Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

7.3.2.1 Hydrochloric acid (rho=1.19g/mL).

7.3.2.2 Hydrogen peroxide (rho=1.10g/mL).

7.3.2.3 Alizarin sulfonate sodium solution (

1.5 g of alizarin sulfonate sodium (C14H7NaO7S) and dissolve it in 300 mL of warm water. Filter, cool, dilute with water to 1000 mL, and mix well.

7.3.2.4 Magnesium chloride solution (420 g/L). Weigh 42 g of magnesium chloride hexahydrate (MgCl2·6H2O), dissolve it in water, and dilute with water to a final concentration of 420 g/L. Mix 100 mL thoroughly. 1 mL of this solution contains 50 mg of magnesium.

7.3.3 Test Procedure

7.3.3.1 Sample Weigh the sample according to Table 18 (Chapter 5), accurate to 0.0001g, and record it as m5.

7.3.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

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

7.3.3.4 Measurement 7.3.3.4.1 Place the sample in a 600mL beaker, cover with a watch glass, and add water and hydrochloric acid in portions according to Table 17 (7.3.2.1). If the sample contains lead... When reacting with bismuth and bismuth, add 1 mL of hydrogen peroxide (7.3.2.2) and let stand for 10 min. After the reaction stops, slowly heat until the sample is completely dissolved. Dissolve, boil for 5 minutes, filter with medium-speed filter paper, wash with hot water, collect the filtrate and washings in a 500 mL volumetric flask (V8), cool, and use... Dilute with water to the mark and mix well. 7.3.3.4.2 When the magnesium alloy does not contain silver, the solution is filtered with medium-speed filter paper, washed with hot water, and the filtrate and washing liquid are collected in a 500 mL volumetric sieve. In a bottle (V8), cool, dilute to the mark with water, and mix well. When the magnesium alloy contains silver, add 50 mL of water and boil for 5 minutes to allow the silver chloride to solidify. After cooling to room temperature, the test solution was filtered through slow-speed filter paper containing filter paper pulp, washed with cold water, and the filtrate and washings were collected in a 500 mL volumetric jar. Place in a bottle (V8), cool, dilute with water to the mark, and mix well.

Note. The residue can be used for the determination of insoluble zirconium (see 7.2).

7.3.4 Experimental Data Processing Calculation results should be retained to three significant figures. Numerical rounding should be performed in accordance with GB/T 8170.

7.3.5 Precision

7.3.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 19, 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 defined using linear data according to Table 19. It can be obtained by interpolation or extension.

7.3.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of average values given in Table 20, represent the two test results. The absolute difference does not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) does not exceed 5%. The reproducibility limit (R) is determined according to the data in Table 20. Obtained by linear interpolation or extrapolation.