GB/T 13748.22-2026Methods for chemical analysis of magnesium and magnesium alloys - Part 22: Determination of thorium content (English PDF)

6.2.3 Hydrochloric acid (1 1). Transfer 500 mL of hydrochloric acid (rho=

1.19 g/mL, analytical grade) to 500 mL of water and mix well.

6.2.4 Hydrochloric acid (1 3). Transfer 500 mL of hydrochloric acid (rho=

1.19 g/mL, analytical grade) and dissolve it in 1500 mL of water, then mix well.

6.2.5 Ammonia (1 3).

6.2.6 Benzoic acid solution (20 g/L). Weigh 10 g of benzoic acid (C6H5COOH) into a 500 mL beaker, add water and heat gently until completely dissolved. (Filter while hot if necessary), dilute to 500 mL, and mix well. Dissolve gently by heating before use.

6.2.7 Benzoic acid cleaning solution (

1.25 g of benzoic acid (C6H5COOH) into a 500 mL beaker, add water and heat gently until dissolved. Cool thoroughly, dilute to 500 mL, and mix well. Filter if necessary.

6.2.8 Saturated oxalic acid solution.

6.2.9 Oxalic acid washing solution. Take 70 mL of saturated oxalic acid solution (6.2.8) and dilute with water to 500 mL.

6.2.10 Bromophenol Blue Solution (4 g/L). Weigh

0.4 g of bromophenol blue (C19H10Br4O5S) into a mortar, add

8.25 mL of sodium hydroxide solution. Grind the liquid (5g/L) until completely dissolved, dilute with water to 100mL, and mix well.

6.3 Test Procedure

6.3.1 Sample Weigh the sample according to Table 1, accurate to 0.0001g, and record it as m0.

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

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

6.3.4 Measurement

6.3.4.1 Place the sample in a 400mL beaker, cover with a watch glass, add 50mL of water, and add hydrochloric acid in portions according to Table 1 (6.2.3). React vigorously. After stopping, boil for 5 minutes. If there are insoluble substances, filter with medium-speed filter paper (when analyzing magnesium alloys containing silver, place a small amount of paper on the filter paper before filtering). Wash the beaker and insoluble matter with hot water, add the washing liquid to the test solution, dilute or evaporate to make the solution volume about 100 mL, and cool.

6.3.4.2 Add 3 drops of bromophenol blue solution (6.2.10) to the test solution [if rare earth elements are present, first add 1g of hydroxylamine hydrochloride (6.2.1)], and then use ammonia water. Adjust the solution to a purple color using (6.2.5) or hydrochloric acid (6.2.4). Add 10g of ammonium chloride (6.2.2), heat to boiling, and while stirring, add 100mL of [amount missing] mL... A benzoic acid solution at a temperature not lower than 80°C (6.2.6) is heated for another 10 minutes. After standing for several minutes, it is filtered while still hot using medium-speed filter paper, and then washed with benzoic acid. Wash the precipitate and filter paper three times each with liquid (6.2.7), and discard the filtrate.

6.3.4.3 Transfer the precipitate back to the original beaker in portions of 50 mL boiling water, and wash it in portions of 10 mL hydrochloric acid (6.2.4) and 50 mL boiling water. Filter paper, combine the filtrates, and boil. Remove and cool, wash the beaker walls, dilute the solution to 125 mL, and slowly add 25 mL while stirring and boil. The saturated oxalic acid solution (6.2.8) was kept at around 80°C for 2 hours and then allowed to stand at room temperature for 12 hours (or overnight).

6.3.4.4 Filter with slow filter paper and wash the precipitate 10 times with oxalic acid washing solution (6.2.9).

6.3.4.5 Place the filter paper and precipitate in a platinum crucible (m2) that has been preheated to constant weight at 950°C, and ashing the filter paper completely in a high-temperature furnace at 500°C. The sample was heated at 950°C for 2 hours, then removed and cooled in a desiccator for 30 minutes before weighing. The heating process was repeated until the difference between two weighings was no greater than [value missing]. 0.0002g, denoted as m1.

6.4 Experimental Data Processing Thorium content is expressed as thorium mass fraction (wTh) and calculated according to formula (1).

6.5 Precision

6.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 2, 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 2. Obtained by interpolation or extrapolation.

6.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of the average values given in Table 3, represent the two test results. 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 calculated using linear regression based on the data in Table 3. It can be obtained by interpolation or extension.

7.2.2 Hydrochloric acid (1 1). Transfer 500 mL of hydrochloric acid (rho=

1.19 g/mL, analytical grade) to 500 mL of water and mix well.

7.2.3 Hydrochloric acid (5 995). Transfer 5 mL of hydrochloric acid (rho=

1.19 g/mL, analytical grade) to 995 mL of water and mix well.

7.2.4 Ammonia (1 4). Take 100 mL of ammonia (7.2.1), dilute with water to 500 mL, and mix well.

7.2.5 Hydroxylamine hydrochloride solution (100 g/L).

7.2.6 Buffer solution. Mix 80 mL of hydrochloric acid (1 47 g/L) and 500 mL of potassium chloride solution (15 g/L).

7.2.7 Zirconium standard solution (

0.5 g/L). Prepare and calibrate as follows, or use a certified standard solution.

a) Preparation. - Weigh 1.7664 g of zirconium oxychloride octahydrate (ZrOCl2·8H2O, analytical grade or purified product) into a 400 mL beaker, add... Add 50 mL of water and.200 mL of hydrochloric acid (7.2.2), heat until completely dissolved, cool to room temperature, and transfer to a 1000 mL volumetric flask. Dilute with water to the mark and mix well; - Weigh 0.6753g of zirconium dioxide (ZrO2, superior grade or purified product) into a platinum crucible, add 4g of potassium pyrosulfate, and incubate at 700°C. Melt for 10-15 minutes, remove and cool, place in a 400mL beaker, add 50mL of water and.200mL of hydrochloric acid. (7.2.2) Heat until completely dissolved, cool to room temperature, transfer to a 1000mL volumetric flask, dilute with water to the mark, and mix well.

b) Calibration. - Mandelic acid gravimetric method. Transfer 100.00 mL of zirconium standard solution (V1) to a 300 mL beaker, add 40 mL of water and Boil 60 mL of hydrochloric acid (7.2.2), then add 50 mL of mandelic acid solution (150 g/L). Maintain the temperature at 80 °C. After 30 minutes, cool and filter using medium-speed filter paper. Use a solution containing 40 mL of hydrochloric acid (7.2.2) and 50 g of mandelic acid per liter. Wash the beaker with a (150 g/L) solution, transfer all the precipitate to filter paper, wash 7-8 times, and place the filter paper in a pre-prepared solution. In a constant-weight platinum crucible (m4), dry and ashed, then ignite at 950°C~1000°C for 2h~3h, remove and place in a desiccator. Cool for 30 minutes and weigh. Repeat the ignition process until constant weight (m3). - Gravimetric method for p-bromomandelic acid. Transfer 100.00 mL of zirconium standard solution (V1) to a 300 mL beaker, add 70 mL of... Water, heated to approximately 80°C, while stirring, slowly add 50 mL of p-bromomandelic acid solution (

0.1 mol/L, weigh out).

11.552 g of p-bromomandelic acid was placed in a beaker,.200 mL of water was added, and the mixture was heated until dissolved. The solution was then transferred to a 500 mL container. In a volumetric flask, dilute to the mark with water and shake well. If precipitate still forms, continue adding p-bromomandelic acid solution until observed. If no precipitate is observed, incubate at 80°C for 30 min, then add 2 mL to 3 mL of p-bromomandelic acid solution to ensure complete precipitation. Stir constantly, cool to room temperature, filter with medium-speed filter paper, wash with water 6-8 times, and place the filter paper in a pre-weighed container. In a platinum crucible (m4), dry and ashed, then ignite at 950°C~1000°C for 2h~3h, remove and cool in a desiccator. After 30 minutes, weigh the product. Repeat the ignition process until constant weight (m3).

7.2.8 Disodium ethylenediaminetetraacetate (EDTA) standard titration solution (

0.010 mol/L). Prepare and standardize as follows, or use... Certified standard solutions.

a) Preparation. Weigh 3.75g of EDTA and dissolve it in water (filter if necessary), transfer it to a 1000mL volumetric flask, and dilute with water to the mark. Mix thoroughly. Store in a plastic bottle.

b) Standardization. Weigh 1.0000g of magnesium (wMg>=99.99%) into a 400mL beaker, add 15mL of water, cover with a watch glass, and aliquot. Add 30 mL of hydrochloric acid (7.2.2) one at a time. After the reaction stops, add

10.00 mL of zirconium standard solution (7.2.7) and boil for 5 minutes. Dilute 30 mL of hydroxylamine hydrochloride solution (7.2.5) with hot water to approximately.200 mL. Heat to a gentle boil, then add 1 mL of xylenol orange. The solution (7.2.9) is boiled again for 2-3 minutes. The temperature is maintained at no less than 85°C, and titrated with EDTA standard titration solution until dissolved. The solution changes from red to yellow; record the volume (V2) of EDTA standard titration solution consumed. After boiling again, the solution color should not change. There have been changes.

c) Calculation. Since the actual concentration of the EDTA standard titration solution may not be 0.01000 mol/L, the correction coefficient is calculated using formula (3). Number (f).

7.2.9 Xylenol orange solution (1 g/L).

7.3 Test Procedure

7.3.1 Sample Weigh 1.00g of sample, accurate to 0.0001g, and record it as m5.

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

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

7.3.4 Measurement

7.3.4.1 Place the sample in a 400mL beaker, add 15mL of water, cover with a watch glass, and add 30mL of hydrochloric acid (7.2.2) in portions [blank]. The experiment involved adding 15 mL of hydrochloric acid (7.2.2). After the vigorous reaction ceased, the mixture was boiled for 5 minutes. If insoluble matter remained, it was filtered through medium-speed filter paper and purified with a solution of at least [missing value]. Wash the beaker and precipitate three times each with hydrochloric acid at 80°C (7.2.3), and add the washing solution to the test solution.

7.3.4.2 Add 30 mL of hydroxylamine hydrochloride solution (7.2.5), add water to a final volume of approximately.200 mL, heat to a gentle boil, and add 1 mL of xylene. Phenol orange solution (7.2.9), boil for 2 to 3 minutes.

7.3.4.3 Keep the solution temperature not lower than 85°C, and slowly add EDTA standard titration solution until the solution changes from red to yellow.

7.3.4.4 Cool to room temperature, add ammonia (7.2.1) until the solution begins to change color. Slowly add ammonia (7.2.4) until the pH value reads on the pH meter is [value missing]. 1.6.

7.3.4.5 Add 10 mL of buffer solution (7.2.6) to turn the solution red, boil, and maintain the solution temperature at no less than 85°C. Use immediately. Titrate with EDTA standard titration solution until the solution changes from red to yellow, and record the volume of EDTA standard titration solution consumed (V3).

7.5 Precision

7.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 4, represent the two test results. 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 determined by linearity of the data in Table 4. Obtained by interpolation or extrapolation.