GB/T 20975.14-2020Methods for chemical analysis of aluminium and aluminium alloys—Part 14: Determination of nickel content (English PDF)

4.1 Method summary

The sample was dissolved with hydrochloric acid. In sodium hydroxide solution, iron is used as carrier to co-precipitate with nickel, filtered, and the precipitate is dissolved in mixed acid. In a Under constant acidity, add tartaric acid, hydroxylamine hydrochloride and sodium thiosulfate to complex interference elements. The complexation of nickel and diacetyl oxime extracted with chloroform And then back-extracted with dilute hydrochloric acid to make nickel into the water phase. Oxidize with bromine water and add dimethylglyoxime to the ammonia solution to make nickel develop.

The absorbance at 445.0nm wavelength of the photometer is measured to determine the nickel content.

4.2 Reagents

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

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

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

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

4.2.4 Ammonia (rho=0.90g/mL).

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

4.2.6 Bromine water (saturated solution).

4.2.7 Ammonia (1 27).

4.2.8 Hydrochloric acid (1 1).

4.2.9 Hydrochloric acid-nitric acid mixed acid. Pipette.200mL nitric acid (4.2.1) and 50mL hydrochloric acid (4.2.8), and mix.

4.2.10 Sulfuric acid (1 1).

4.2.11 Hydrochloric acid (1 5).

4.2.12 Hydrochloric acid (1 23).

4.2.13 Sodium hydroxide solution (250g/L), stored in plastic bottles.

4.2.14 Sodium hydroxide solution (2g/L).

4.2.15 Tartaric acid solution (300g/L).

4.2.16 Ferric chloride solution (1mg/mL). Weigh 0.48g iron trichloride (FeCl3·6H2O) or 0.3g iron trioxide (FeCl3) to dissolve In 5mL hydrochloric acid (4.2.8), dilute to 100mL with water, and mix.

4.2.17 Hydroxylamine hydrochloride solution (100g/L), ready when used.

4.2.18 Sodium thiosulfate solution (500g/L).

4.2.19 Diacetyl oxime ethanol solution (10g/L).

4.2.20 Trichloromethane.

4.2.21 Nickel standard storage solution A. Weigh 1.0000g nickel (wNi>=99.99%), place it in a 250mL beaker, add 10mL water and 10mL nitric acid (4.2.1), heat until the nickel is completely dissolved, add 10mL hydrochloric acid (4.2.2), heat to evaporate to dryness (can not be scorched), then add 10mL hydrochloric acid (4.2.2), continue to heat and evaporate to dryness. Add 20mL hydrochloric acid (4.2.2) and heat to dissolve the salts, then transfer to 1000mL volume. In a measuring flask, let cool. Dilute to the mark with water and mix well. This solution 1mL contains 1mg nickel.

4.2.22 Nickel standard solution A. Pipette 10.0mL nickel standard stock solution A (4.2.21) into a 1000mL volumetric flask and dilute with water to Mix well, this solution 1mL contains 0.01mg nickel.

4.3 Apparatus

4.3.1 Spectrophotometer.

4.3.2 Acidity meter.

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 a sample (4.4) with a mass (m) of 1.00g, accurate to 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 400mL beaker, slowly add 25mL of hydrochloric acid (4.2.8), and cover with a watch glass. Wait for violent reaction to stop After stopping, heat until the sample is completely dissolved. If the sample is difficult to dissolve, you can add an appropriate amount of hydrogen peroxide (4.2.5) to completely dissolve the sample and heat it to decompose Excessive hydrogen peroxide. Dilute with water to about 80mL, filter with slow quantitative filter paper, wash with hot water, and collect the filtrate and washing liquid in 400mL beaker.

4.5.4.2 Move the filter paper and residue into a platinum crucible, dry it and ash completely (do not burn the filter paper) and cool. Add 1mL~2mL sulfuric acid (4.2.10), 5mL hydrofluoric acid (4.2.3), and then dropwise add nitric acid (4.2.1) until the solution is clear, heat and evaporate until the sulfuric acid fumes are removed. Burn (<=700°C) 10min, cool, add a few milliliters of hot water and 1mL~2mL hydrochloric acid (4.2.8), slightly heat to dissolve the salts, incorporate this solution The main filtrate (4.5.4.1) is diluted with water to about 150mL.

4.5.4.3 Add 0.5mL ferric chloride solution (4.2.16) (if the mass fraction of iron in the sample is greater than 0.2%, it is not necessary to add ferric chloride solution Solution) and 45mL sodium hydroxide solution (4.2.14), the test solution is heated to 70 °C ~ 90 °C and kept for 20 minutes, then boil for 2 minutes ~ 3 minutes.

4.5.4.4 Filter with a fritted glass funnel (phi4.5µm~phi9µm) and wash immediately with hot sodium hydroxide solution (4.2.14). will Mix 10 mL of hot hydrochloric acid-nitric acid mixed acid (4.2.9) with 10 mL of hot water, use it to dissolve the precipitate on the funnel in the original beaker, and then use the hot Wash with water. Heat to dissolve the salts completely, and cool down. Transfer the test solution to a.200mL volumetric flask (V1), dilute to the mark with water, and mix.

Pipette volume (V2) of 50mL test solution (4.5.4.4) into a 150mL beaker.

4.5.4.5 Add 10mL tartaric acid solution (4.2.15), 5mL hydroxylamine hydrochloride solution (4.2.17), add sodium hydroxide to dissolve under constant stirring The solution (4.2.13) is adjusted to pH 4.5~5.0. Add 10mL sodium thiosulfate solution (4.2.18), and use sodium hydroxide solution under stirring [(4.2.13) and (4.2.14)] adjusted to pH 6.5. Transfer the test solution into a 250mL separatory funnel and wash with as little water as possible.

4.5.4.6 Add 5mL of diacetyl oxime ethanol solution (4.2.19) and mix well. Add 10mL chloroform (4.2.20), shake for 2min, layered. Transfer the organic phase to the second 100mL separatory funnel, wash with 1mL~2mL chloroform (4.2.20) (without shaking) water Put the phases into a separatory funnel containing the organic phase. Add 5mL of trichloromethane (4.2.20) to the water phase, shake for 30s, and stand still for layering.

The organic phase was also transferred to the second separatory funnel. Use 5mL chloroform (4.2.20) to extract once, and combine the organic phases. Discard the water phase.

4.5.4.7 In the second separatory funnel containing the organic phase, add 20mL ammonia (4.2.7), shake for 30s, and let stand for layering. Organic phase Transfer to the third 100mL separatory funnel. Wash with 1mL~2mL chloroform (4.2.20). The organic phase is combined in the third split In the funnel, the water phase is stored in the second separatory funnel.

4.5.4.8 In the third separatory funnel containing the organic phase, add 20mL ammonia (4.2.7), shake for 30s, and let stand for layering. Organic phase Transfer to the fourth 100mL separatory funnel. Wash with 1mL~2mL chloroform (4.2.20). The organic phase is combined in the fourth split In the funnel, move the water phase into the second separatory funnel and wash with 5mL chloroform (4.2.20), shaking for 30s. Stand still and layer, release there The machine phase is in the fourth separatory funnel. Then wash with 1mL~2mL trichloromethane (4.2.20). Combine the organic phases and discard the aqueous phase.

4.5.4.9 In the fourth separatory funnel containing the organic phase, add 20 mL of hydrochloric acid (4.2.12), shake for 30 seconds, and stand for separation. Will be organic The phase shifted into the fifth 100 mL separatory funnel. Wash with 1mL~2mL chloroform (4.2.20). The organic phase is combined and the water phase is stored in The fourth separatory funnel. The organic phase was treated twice with 10 mL of hydrochloric acid (4.2.12) each time, and separated after each treatment. Organic phase Transfer to the sixth and seventh separatory funnels respectively. Wash with 1mL~2mL chloroform (4.2.20) respectively, and collect all water phases in The fourth separatory funnel. After the third treatment, the organic phase was discarded.

4.5.4.10 In the fourth separatory funnel containing the water phase, add 5mL chloroform (4.2.20), shake for 30s, and stand for stratification. Discard The organic phase. Then add 5mL chloroform (4.2.20), shake for 30s, and stand to separate layers. Carefully release the organic phase and discard it.

4.5.4.11 Move the water phase into a 100mL volumetric flask, wash carefully with water, add 10mL hydrochloric acid (4.2.11), and dilute with water to about 80mL. Heat to 35 °C ~ 40 °C, in constant shaking, dropwise add bromine water (4.2.6) until orange-yellow appears, then excess 2mL, and cool.

Slowly add ammonia (4.2.4) while shaking until the color disappears and an excess of 1 mL, cool. Add 1mL of diacetyl oxime ethanol solution (4.2.19), Dilute to the mark with water and mix well. The absorbance was measured after being placed for 30 minutes and completed within 60 minutes.

4.5.4.12 Move a part of the test solution (4.5.4.11) into the absorption cell, and use the blank test solution (4.5.3) made with the sample as a reference.

The absorbance was measured at a wavelength of 445.0nm with a photometer. Find the corresponding nickel mass (m1) from the working curve.

4.6 Drawing of working curve

4.6.1 Pipette 0mL, 0.50mL, 1.00mL, 2.00mL, 5.00mL, 10.00mL nickel standard solution A (4.2.22) into a set of dry In a dry 150mL beaker, dilute with water to about 40mL. The following shall be carried out according to 4.5.4.5~4.5.4.11.

4.6.2 Move part of the solution (4.6.1) into the absorption cell, take the reagent blank solution as a reference, and measure at the wavelength of the spectrophotometer at 445.0nm The absorbance, the nickel mass as the abscissa and the absorbance as the ordinate, draw the working curve.

4.7 Test data processing

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

Where.

m1---The quality of nickel found on the working curve, in milligrams (mg);

V1---The total volume of the test solution, in milliliters (mL);

m ---the mass of the sample, in grams (g);

V2--Divide the volume of the test solution in milliliters (mL).

The calculation result retains two significant digits. The rounding of values shall be implemented in 3.2 and 3.3 of GB/T 8170-2008.

4.8 Precision

4.8.1 Repeatability

The measured values of two independent test results obtained under repeatability conditions are within the average range given in Table 1. 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.

4.8.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions are within the average range given in Table 2. These two test results The absolute difference does not exceed the reproducibility limit R, and the reproducibility limit R does not exceed 5%. The reproducibility limit R is linear according to the data in Table 2. Obtained by interpolation or extension.

5.1 Method summary

The sample is dissolved with hydrochloric acid and hydrogen peroxide, and the nickel is measured with an air-acetylene lean flame at the wavelength of 232.0nm in the atomic absorption spectrometer. The absorbance is used to determine the nickel 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%, wNi<=0.0003%).

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

5.2.3 Hydrofluoric acid (rho=1.14g/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 matrix solution (20mg/mL). Weigh 20.00g of pure aluminum (5.2.1) and place it in a 1000mL beaker. 600mL hydrochloric acid (5.2.5), covered with a watch glass. 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, decompose excess hydrogen peroxide, and cool. Transfer the solution into a 1000mL volumetric flask, dilute to the mark with water, Mix well.

5.2.8 Nickel standard storage solution B. Weigh 1.0000g nickel (wNi>=99.99%), place it in a 400mL beaker, add 50mL hydrochloric acid (5.2.5), drop an appropriate amount of hydrogen peroxide (5.2.4), cover with a watch glass, slowly heat to completely dissolve the nickel, boil for a few minutes to decompose the excess peroxide Hydrogen, cooling. Add 20mL hydrochloric acid (5.2.5) and heat to dissolve the salts, transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix uniform. This solution 1mL contains 1mg nickel.

5.2.9 Nickel standard solution B. Pipette 20.00mL nickel standard stock solution B (5.2.8) into a 50mL volumetric flask and dilute to the mark with water. Mix well. 1mL of this solution contains 0.4mg of nickel.

5.2.10 Nickel standard solution C. Pipette 10.00mL nickel standard stock solution B (5.2.8) into a 100mL volumetric flask, dilute with water to Degree, mix well. This solution 1mL contains 0.1mg nickel.

5.2.11 Nickel standard solution D. Pipette 5.00mL nickel standard stock solution B (5.2.8) into a 100mL volumetric flask and dilute to the mark with water. Mix well. 1mL of this solution contains 0.05mg of nickel.

5.3 Apparatus

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

---Characteristic concentration. In a solution consistent with the matrix of the measurement sample solution, the characteristic concentration of nickel should not be greater than 0.1µg/mL.

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

---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 the mass (m2) as 1.00g sample (5.4), 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, add about 10mL of water, and add 30mL of hydrochloric acid (5.2.5) in batches.

Cover the watch glass. After the violent reaction stops, slowly heat until the sample is completely dissolved. Add an appropriate amount of hydrogen peroxide (5.2.4) dropwise, boil for 10 minutes, cool down. If there is insoluble matter, filter and wash. Place the residue and filter paper in a platinum crucible, ash (do not burn the filter paper), and burn at about 550°C Burn and cool. Add 2mL sulfuric acid (5.2.6), 5mL hydrofluoric acid (5.2.3), add nitric acid (5.2.2) dropwise until the solution is clear. Heat to evaporate to dryness, Burn at 700°C for a few minutes and cool. Dissolve the residue with as little hydrochloric acid (5.2.5) as possible (filter if necessary), combine this test solution with the original filter In the liquid.

5.5.4.2 Transfer the test solution (5.5.4.1) into a 100mL volumetric flask (V3).

5.5.4.3 According to the mass fraction of nickel, pipette the corresponding volume (V4) of the test solution (5.5.4.2) into a 100mL volumetric flask (V5) according to Table 3.

Dilute to the mark and mix well.

5.5.4.4 Place the blank test solution (5.5.3) and test solution (5.5.4.3) at the wavelength of 232.0nm of the atomic absorption spectrometer, and use air-acetylene lean The flammable flame is adjusted to zero with water, the absorbance is measured, and the nickel mass concentration (rho0, rho1) is found from the working curve.

5.5.5 Drawing of working curve

5.5.5.1 According to the mass fraction of nickel in the sample, the preparation of the working curve series standard solution is divided into 3 types.

a) When the nickel mass fraction is 0.0050%~0.050%. pipette 0mL, 1.00mL, 2.00mL, 5.00mL, 8.00mL, 10.00mL Nickel standard solution D (5.2.11) is placed in a set of 100mL volumetric flasks, and 50mL aluminum matrix solution (5.2.7) is added to each to Dilute with water to the mark and mix well;

b) When the mass fraction of nickel is >0.050%~0.50%. pipette 0mL, 1.00mL, 2.00mL, 5.00mL, 8.00mL, 10.00mL Nickel standard solution C (5.2.10) was placed in a set of 100mL volumetric flasks, and 10mL aluminum matrix solution (5.2.7) was added to each to Dilute with water to the mark and mix well;

c) When the mass fraction of nickel is >0.50%~3.00%. pipette 0mL, 1.00mL, 2.00mL, 5.00mL, 8.00mL, 10.00mL nickel Standard solution B (5.2.9) was placed in a set of 100mL volumetric flasks, and 5mL aluminum matrix solution (5.2.7) was added to each, diluted with water Release to the mark and mix well.

5.5.5.2 Measurement