GB/T 20975.3-2020Methods for chemical analysis of aluminium and aluminium alloys—Part 3: Determination of copper content (English PDF)

4.1 Method summary

The sample is dissolved in hydrochloric acid and nitric acid, and the divalent copper ions are reduced to monovalent copper ions with hydroxylamine hydrochloride, and extracted with chloroform at about pH 4.5 Take the colored complex formed by new cuprous spirit and monovalent copper ion, and measure its absorbance at a wavelength of 460.0nm with a spectrophotometer to determine Copper content.

4.2 Reagents and materials

Unless otherwise stated, only reagents and laboratory secondary water confirmed to be analytically pure are used in the analysis.

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

4.2.2 Trichloromethane.

4.2.3 Hydrochloric acid (1 1).

4.2.4 Nitric acid (1 1).

4.2.5 Sulfuric acid (1 1).

4.2.6 Ammonia (1 1).

4.2.7 Hydroxylamine hydrochloride solution (100g/L).

4.2.8 Ammonium citrate solution (500g/L).

4.2.9 Neocuproine ethanol solution (1g/L). Weigh 0.1g of 2,9-dimethyl-1,10-phenanthroline in a beaker and dilute with absolute ethanol to 100mL (placed overnight).

4.2.10 Copper standard storage solution. Weigh 1.0000g copper (wCu>=99.99%) and place it in pre-filled with 20mL water and 10mL nitric acid (4.2.4) in the 400mL beaker, cover with a watch glass, after the dissolution is complete, place it on a water bath to evaporate until the crystals Into a 1000mL volumetric flask, mix well. This solution 1mL contains 1mg copper.

4.2.11 Copper standard solution. Pipette 5.00mL copper standard stock solution (4.2.10) into a 500mL volumetric flask, dilute to the mark with water, Mix well. 1mL of this solution contains 0.01mg of copper.

4.2.12 Congo red test paper.

4.3 Apparatus

Spectrophotometer.

4.4 Sample

Process the sample into chips with a thickness of not more than 1mm.

4.5 Analysis steps

4.5.1 Sample

Weigh the sample (4.4) with a mass (m0) of 0.50g to the nearest 0.0001g.

4.5.2 Parallel test

Do two tests in parallel and take the average value.

4.5.3 Blank test

Do a blank test with the sample (4.5.1).

4.5.4 Determination

4.5.4.1 Place the sample (4.5.1) in a 250mL beaker, add 5mL water and 15mL hydrochloric acid (4.2.3). After the sample is completely dissolved Add 2mL nitric acid (4.2.4), heat and boil for 2min~3min to drive off nitrogen oxides (the blank evaporates to about 2mL), wash with a small amount of water The wall of the cup is cooled to room temperature. Filter with slow-speed filter paper (if clear, not filter). Wash the filter paper and residue 8 times with hot hydrochloric acid (4.2.3)~ 10 times. Collect the filtrate and washing liquid in a 400mL beaker. If there is a large amount of residue, place the filter paper and the residue in a platinum crucible. Ash completely at 550°C (do not burn), and cool down. Add 2mL sulfuric acid (4.2.5) and 5mL hydrofluoric acid (4.2.1), add nitric acid dropwise (4.2.4) until the solution is clear. Heat to evaporate until sulfuric acid fumes, burn at 700°C for 10min (not exceeding 700°C), and cool. Join as little as possible Hydrochloric acid (4.2.3) and a few milliliters of water, heated to completely dissolve the precipitate (if turbidity needs to be filtered), combine this solution in the main test solution.

4.5.4.2 Add 8mL ammonium citrate solution (4.2.8), 5mL hydroxylamine hydrochloride solution (4.2.7) to the test solution, mix well, and add 5mL Xinya Copper spirit ethanol solution (4.2.9), put in a small piece of Congo red test paper (4.2.12), use ammonia (4.2.6) to adjust the Congo red test paper to red, then use Then continue to carefully adjust the pH test paper to a pH value of about 4.5, transfer the test solution into a 250mL separatory funnel, make the volume about 60mL~70mL, add 10.00mL chloroform (4.2.2) was extracted for 2min.

4.5.4.3 Transfer part of the test solution of the organic phase into a 1cm absorption cell, use chloroform (4.2.2) as a reference, and set it at the wavelength of the spectrophotometer. Measure the absorbance at 460.0nm, subtract the absorbance of the blank test solution from the measured absorbance, and check the corresponding Copper quality (m1).

4.5.5 Drawing of working curve

Pipette 0mL, 0.50mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, 5.00mL, 6.00mL copper standard solution (4.2.11) In a set of 250mL beakers, add 20mL water and 3mL hydrochloric acid (4.2.3), and mix well. The following shall be carried out according to 4.5.4.2, without adjustment For pH value, the reagent blank solution is used as a reference, and its absorbance is measured at a wavelength of 460.0nm on a spectrophotometer. Take the amount of copper as the abscissa, suck The luminosity is the ordinate, and the working curve is drawn.

4.6 Test data processing

The copper content is calculated as the copper mass fraction wCu, calculated according to formula (1).

When the copper mass fraction is >=0.0010%, the calculation result retains two significant digits; when the copper mass fraction is less than 0.0010%, the calculation result is retained A valid number. The rounding of values shall be implemented in 3.2 and 3.3 of GB/T 8170-2008.

4.7 Precision

4.7.1 Repeatability

The measured values of two independent test results obtained under repeatability conditions, within the average range given below, these two test results The absolute difference does not exceed the repeatability limit r, and the case of exceeding the repeatability limit r does not exceed 5%. The repeatability limit r is within the linear range according to the data in Table 1. Obtained by interpolation or extension method.

4.7.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions, within the average range given below, the two test results The absolute difference is not greater than the reproducibility limit R, and the case of exceeding the reproducibility limit R does not exceed 5%. Reproducibility limit R is linear within Obtained by interpolation or extension method.

5.1 Method summary

The sample is dissolved in hydrochloric acid and hydrogen peroxide, and the wavelength of the atomic absorption spectrometer is 324.7nm. Air-acetylene (or nitrous oxide-ethane The alkyne) lean flame measures the copper absorbance to determine the copper content.

5.2 Reagents

Unless otherwise stated, only reagents and laboratory secondary water confirmed to be analytically pure are used in the analysis.

5.2.1 Pure aluminum (wAl>=99.99%, wCu<=0.0010%).

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

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

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

5.2.5 Hydrochloric acid (1 1).

5.2.6 Sulfuric acid (1 1).

5.2.7 Aluminum solution (20mg/mL). Weigh 20.00g pure aluminum (5.2.1) into a 1000mL beaker, cover with a watch glass, and add the total amount in portions It is 600mL of hydrochloric acid (5.2.5). After the violent reaction stops, slowly heat to complete dissolution, and then add a few drops of hydrogen peroxide (5.2.4), Boil for a few minutes to decompose excess hydrogen peroxide and cool. Transfer the solution into a 1000mL volumetric flask, dilute to the mark with water, and mix.

5.2.8 Copper standard storage solution. Weigh 1.000g of copper (wCu>=99.95%), place it in a 250mL beaker, cover with a watch glass, and add 5mL nitrate Acid (5.2.3), slowly heat until completely dissolved, and cool. Transfer the solution into a 1000mL volumetric flask, dilute to the mark with water, and mix. This melt Liquid 1mL contains 1mg copper.

5.2.9 Copper standard solution A. Pipette 100.00mL copper standard stock solution (5.2.8) into a 1000mL volumetric flask, dilute with water to Degree, mix well (prepared when used). This solution 1mL contains 0.1mg copper.

5.2.10 Copper standard solution B. Pipette 50.00mL copper standard stock solution (5.2.8) into a 1000mL volumetric flask, dilute with water to Degree, mix well (prepared when used). 1mL of this solution contains 0.05mg copper.

5.3 Apparatus

Atomic absorption spectrometer with copper hollow cathode lamp. The instrument should meet the following conditions.

---Characteristic concentration. In the solution consistent with the measurement sample solution matrix, the characteristic concentration of copper should not be greater than 0.033µg/mL;

---Precision. Use the highest concentration of standard solution to measure absorbance 10 times, and its standard deviation should not exceed the average value of absorbance 1.0%, use the lowest concentration standard solution (not zero concentration solution) to measure the absorbance 10 times, and the standard deviation should not exceed the highest 0.5% of the average absorbance of the concentration standard solution;

---Linear working curve. Divide the working curve into five equal sections according to the concentration, the difference between the absorbance difference of the highest section and the absorbance difference of the lowest section The ratio should not be less than 0.70.

5.4 Sample

Process the sample into chips with a thickness of not more than 1mm.

5.5 Analysis steps

5.5.1 Sample

Weigh a sample (5.4) with a mass (m2) of 1.00g, accurate to 0.0001g.

5.5.2 Parallel test

Do two tests in parallel and take the average value.

5.5.3 Blank test

Weigh 1.00g pure aluminum (5.2.1) instead of the sample (5.5.1), and do a blank test with the sample.

5.5.4 Determination

5.5.4.1 Place the sample (5.5.1) in a 250mL beaker, cover with a watch glass, add about 10mL of water, and add 30mL of hydrochloric acid in batches. (5.2.5), after the violent reaction stops, slowly heat until the sample is completely dissolved. Add appropriate amount of hydrogen peroxide (5.2.4) dropwise, heat to boil 10min to remove excess hydrogen peroxide and cool.

5.5.4.2 If any insoluble matter needs to be filtered and washed with quantitative filter paper, keep this solution as the main filtrate, put the residue together with filter paper in a platinum crucible, Melt (don't burn the filter paper), burn at about 550°C, and cool. Add 2mL sulfuric acid (5.2.6) and 5mL hydrofluoric acid (5.2.2), and add dropwise Add nitric acid (5.2.3) until the solution is clear (about 1mL), heat and evaporate to dryness. Burn at about 700°C for 10 minutes and cool. Use as little salt as possible Acid (5.2.5) and a small amount of water to dissolve the residue (filter if necessary), and combine this solution in the main filtrate.

5.5.4.3 According to Table 3, transfer the test solution or the combined test solution after treatment of insolubles into the corresponding volumetric flask, dilute to the mark with water, and mix.

5.5.4.4 According to Table 3, pipette the corresponding volume of test solution into the corresponding volumetric flask, add the corresponding volume of hydrochloric acid (5.2.5), and dilute to the mark with water. Mix well. Put the blank test solution and test solution at the wavelength of 324.7nm in the atomic absorption spectrometer, use the air-acetylene lean flame, and adjust the zero with water. Measure the absorbance of copper. Use the absorbance of the test solution (minus the absorbance of the blank test solution) to find the corresponding copper mass concentration (rho) from the working curve.

5.5.5 Drawing of working curve

5.5.5.1 According to the mass fraction of copper in the sample, the preparation of the series of standard solutions is divided into the following 4 types.

a) When the mass fraction of copper is 0.0050%~0.050%, pipette 0mL, 1.00mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL, 10.00mL copper standard solution B (5.2.10), respectively placed in a set of 100mL volumetric flasks, add 50.0mL aluminum Solution (5.2.7), dilute to the mark with water, and mix;

b) When the copper mass fraction is >0.050%~0.50%, pipette 0mL, 1.00mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL, 10.00mL copper standard solution B (5.2.10), respectively placed in a set of 100mL volumetric flasks, add 5.0mL aluminum Solution (5.2.7), dilute to the mark with water, and mix;

c) When the copper mass fraction is >0.50%~5.00%, pipette 0mL, 2.00mL, 4.00mL, 8.00mL, 12.00mL, 16.00mL, 20.00mL copper standard solution A (5.2.9), respectively placed in a set of 100mL volumetric flasks, add 2.0mL aluminum The solution (5.2.7) and 10 mL of hydrochloric acid (5.2.5) are diluted with water to the mark, and mixed;

d) When the copper mass fraction is >5.00%~8.00%, pipette 0mL, 4.00mL, 5.00mL, 6.00mL, 7.00mL, 8.00mL Copper standard solution A (5.2.9), respectively placed in a set of 250mL volumetric flasks, add 0.5mL aluminum solution (5.2.7), 25mL salt Acid (5.2.5), dilute to the mark with water, and mix well.

5.5.5.2 Put a series of standard solutions (5.5.5.1) at the wavelength of 324.7nm in the atomic absorption spectrometer, use an air-acetylene lean flame, and use water Adjust zero to measure the absorbance of a series of standard solutions. Take the mass concentration of copper as the abscissa, and the absorbance (minus the absorbance of the "zero" concentration solution) as The ordinate, draw the working curve.

5.6 Test data processing

The copper content is calculated as the copper mass fraction wCu, calculated according to formula (2).

5.7 Precision

5.7.1 Repeatability

The measured values of two independent test results obtained under repeatability conditions, within the average range given below, these two test results The absolute difference does not exceed the repeatability limit r, and the case of exceeding the repeatability limit r does not exceed 5%. The repeatability limit r is within the linear range according to the data in Table 4 Obtained by interpolation or extension method.

5.7.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions, within the average range given below, the two test results The absolute difference is not greater than the reproducibility limit R, and the case of exceeding the reproducibility limit R does not exceed 5%. Reproducibility limit R is linear within Obtained by interpolation or extension method.

6.1 Method summary

The sample is decomposed with hydrochloric acid and nitric acid. In the presence of fluoride, sulfuric acid is used to drive off silicon and nitric acid, and then ammonium bifluoride at pH 3.0~4.0 In the solution, copper (II) reacts with potassium iodide to form cuprous iodide and precipitates the amount of iodine, which is titrated with sodium thiosulfate standard solution to calculate The copper content.

6.2 Reagents

Unless otherwise stated, only reagents and laboratory secondary water confirmed to be analytically pure are used in the analysis.

6.2.1 Anhydrous sodium carbonate.

6.2.2 Hydrochloric acid (11).

6.2.3 Nitric acid (1 1).

6.2.4 Sulfuric acid (11).

6.2.5 Sulfuric acid (1 17).

6.2.6 Ammonia (1 1).

6.2.7 Potassium thiocyanate (100g/L). Weigh 10g of potassium thiocyanate and dissolve it in 50mL of water, dilute to 100mL, and filter if necessary.

6.2.8 Ammonium bifluoride solution (200g/L). Weigh.200g of ammonium bifluoride, dissolve it in 800mL of water, dilute to 1000mL, and store in polyethylene In the bottle.

6.2.9 Potassium iodide solution (200g/L). Weigh.200g of potassium iodide and dissolve it in 800mL of water, dilute to 1000mL, and place it in a brown reagent bottle Store in a dark place.

6.2.10 Potassium dichromate standard solution [c(1/6K2Cr2O7)=0.1000mol/L]. Weigh 4.9030g benchmark potassium dichromate (previously dried at 140°C for 2h and cooled to room temperature in a desiccator) and placed it in 300mL Dissolve in water in the cup, transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix well.

6.2.11 Sodium thiosulfate standard titration solution (c1~0.1mol/L).

---Preparation. Weigh 26g sodium thiosulfate (Na2S2O3.5H2O) or 16g anhydrous sodium thiosulfate (Na2S2O3) and dissolve it in hot water, cold After cooling, transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix well.

---Calibration. Pipette 20.00mL potassium dichromate standard solution (6.2.10) into a 500mL Erlenmeyer flask, add 10mL potassium iodide (6.2.9) and 20mL sulfuric acid (6.2.5), mix well, place in a dark place for 10 minutes, add 50mL water, and use the prepared sodium thiosulfate Titrate with the standard titration solution. When near the end point (yellow-green), add 5mL starch indicator (6.2.12), and continue the titration until the solution turns from blue to blue. The color changes to bright green, and the consumption of sodium thiosulfate standard titration solution volume V3 is recorded. Do a blank test at the same time.

---Calculation. Calculate the concentration of sodium thiosulfate standard solution by formula (3).

6.2.12 Starch indicator (5g/L). Weigh 1g of starch and moisten it with water, add.200mL of boiling water, and cook until it is transparent and cool, and it is ready to use.

6.3 Sample

Process the sample into chips with a thickness of not more than 1mm.

6.4 Analysis steps

6.4.1 Sample

Weigh the mass (m3) of the sample (6.3) according to Table 6, accurate to 0.0001g.

6.4.2 Parallel test

Do two tests in parallel and take the average value.

6.4.3 Determination

6.4.3.1 Place the sample (6.4.1) in a 500mL conical cup, add hydrochloric acid (6.2.2) according to Table 6, and heat to dissolve until copper powder or copper flakes appear After adding 2.5mL ammonium bifluoride solution (6.2.8) and 10mL nitric acid (6.2.3), continue to heat until the sample is completely dissolved. […]