GB/T 20975.12-2020Methods for chemical analysis of aluminium and aluminium alloys—Part 12: Determination of titanium content (English PDF)

4.1 Method summary

The sample is dissolved in hydrochloric acid and hydrogen peroxide, and ascorbic acid is used to reduce interference ions such as Fe3 and V5 in the presence of copper sulfate. In sulfuric acid In the medium, add diantipyrylmethane solution to develop color, and measure the absorbance of the solution at the wavelength of 400.0nm in the spectrophotometer to determine the titanium 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 Sulfuric acid (rho=1.84g/mL).

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

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

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

4.2.5 Sulfuric acid (1 1).

4.2.6 Hydrochloric acid (1 1).

4.2.7 Copper sulfate solution (50g/L).

4.2.8 Ascorbic acid solution (20g/L), prepared immediately when used.

4.2.9 Diantipyrylmethane solution (50g/L). Dissolve 5g of diantipyrylmethane in about 17mL of hydrochloric acid (4.2.6) and 70mL of water Alkane, diluted to 100mL with water and mixed.

4.2.10 Aluminum solution (10mg/mL). Weigh 10.00g pure aluminum (wAl>=99.99%, wTi<=0.0010%) into a.200mL beaker, Cover the watch glass. Add 300mL hydrochloric acid (4.2.6) in batches, and slowly heat until the aluminum is completely dissolved. Take it off and let it cool. Move into 1000mL In a volumetric flask, dilute to the mark with water and mix well.

4.2.11 Titanium standard storage solution. Weigh 0.1000g metallic titanium (wTi>=99.9%), add 50mL sulfuric acid in a 300mL beaker (4.2.5) and 10mL of hydrochloric acid (4.2.6), add 1mL of nitric acid (1 1) after heating to decompose, heat until the titanium is completely dissolved, and continue to heat to evaporate When the white smoke has just come out, remove it, cool it, carefully add about 10mL of water, dissolve the soluble salts, cool to room temperature, and transfer to a 1000mL volumetric flask Dilute to the mark with water and mix well. 1mL of this solution contains 0.1mg of titanium.

4.2.12 Titanium standard solution A. Pipette 50.00mL titanium standard stock solution (4.2.11) into a 500mL volumetric flask and dilute to the mark with water. Mix well (prepared when used). 1mL of this solution contains 0.01mg of titanium.

4.3 Apparatus

Spectrophotometer.

4.4 Sample

Process the sample into chips with a thickness not exceeding 1 mm.

4.5 Analysis steps

4.5.1 Sample

Weigh the mass (m0) to 0.50g sample (4.4), accurate to 0.0001g.

4.5.2 Parallel test

Do two tests in parallel and take the average value.

4.5.3 Determination

4.5.3.1 Place the sample (4.5.1) in a 250mL beaker, add 15mL of water, add 15mL of hydrochloric acid (4.2.6) in batches, drop by Add 1.5mL hydrogen peroxide (4.2.4) or 0.5mL nitric acid (4.2.2), cover with a watch glass, slightly heat to dissolve the sample completely, boil for about 10min, use Rinse the watch glass and cup wall with water, remove and cool. Transfer to a 100mL volumetric flask (V0), dilute to the mark with water, and mix. If there is insoluble matter (silicon Etc.) Then filter in a 100mL volumetric flask (V0), put the precipitate and filter paper in a platinum crucible, ash (do not burn the filter paper), burn at 550°C Boil for 30min, take out, and cool. Add 2mL sulfuric acid (4.2.1), 5mL hydrofluoric acid (4.2.3), dropwise add nitric acid (4.2.2) until the test solution is clear, steam Let it dry, burn it at 700°C for a few minutes, take it out, and cool. Use a small amount of hydrochloric acid (4.2.6) to dissolve the residue (filter if it is turbid), and combine In a 100mL volumetric flask (V0), dilute to the mark with water and mix well.

4.5.3.2 Pipette two portions of the test solution (4.5.3.1) of the corresponding volume (V1) according to Table 1, and place them in a 100mL volumetric flask, and add the corresponding volume Aluminum solution (4.2.10). Add 25mL sulfuric acid (4.2.5), add water to about 80mL, add 2 drops of copper sulfate solution (4.2.7), 2mL ascorbic acid Blood acid solution (4.2.8), mix well.

4.5.3.3 One part does not add diantipyrylmethane solution (4.2.9), this is the compensation solution; the other part is added with 10mL diantipyrylmethane solution Alkane solution (4.2.9). After cooling the two solutions to room temperature, dilute to the mark with water and mix well. Leave it for 30 minutes.

4.5.3.4 Move a part of the solution (4.5.3.3) into the absorption cell, use the compensation solution as the reference solution, and measure at 400.0nm of the spectrophotometer Absorbance, check the corresponding amount of titanium (m1) from the working curve.

4.5.4 Drawing of working curve

4.5.4.1 According to the titanium mass fraction in the sample, the preparation of the series of standard solutions is divided into the following two types.

a) When the titanium mass fraction is 0.0010%~0.010%. pipette 0mL, 0.25mL, 0.50mL, 1.00mL, 2.00mL, 3.00mL titanium standard solution A (4.2.12) in a set of 100mL volumetric flasks, respectively add 25.0mL aluminum solution (4.2.10);

b) When the titanium mass fraction is >0.010%~0.50%. pipette 0mL, 2.00mL, 4.00mL, 8.00mL, 12.00mL, 16.00 mL titanium standard solution A (4.2.12) was put into a set of 100 mL volumetric flasks, and 25.0 mL aluminum solution Liquid (4.2.10).

4.5.4.2 Add 25mL sulfuric acid (4.2.5), add water to about 80mL, add 2 drops of copper sulfate solution (4.2.7), 2mL ascorbic acid solution (4.2.8), mix well; then add 10mL diantipyrimethane solution (4.2.9), after the solution is cooled to room temperature, dilute to the mark with water, mix uniform. Leave it for 30 minutes.

4.5.4.3 Move part of the series of standard solutions (4.5.4.1) into the absorption tank, and use the reagent blank solution (without the titanium standard solution) as a reference.

Measure the absorbance at 400.0nm with a spectrophotometer, and draw the working curve with the amount of titanium as the abscissa and absorbance as the ordinate.

4.6 Test data processing

The titanium content is calculated as the mass fraction wTi of titanium and calculated according to formula (1).

The calculation result retains two significant digits, and the numerical rounding is performed in accordance with 3.2 and 3.3 of GB/T 8170-2008.

4.7 Precision

4.7.1 Repeatability

The measured value 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 repeatability limit r does not exceed 5%. The repeatability limit r is within the linear range according to the data in Table 2. Obtained by interpolation or extension method.

4.7.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions are within the average range given below. 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 3. Obtained by interpolation or extension.

5.1 Method summary

The sample is dissolved in sodium hydroxide solution, neutralized to acidity with a mixed acid of sulfuric acid and nitric acid, and hydrogen peroxide is added to make it color, and then the spectrophotometer At a wavelength of 410.0nm, measure the absorbance of the solution to determine the titanium 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 Sodium hydroxide solution (400g/L), stored in a polyethylene bottle.

5.2.2 Nitric acid (11).

5.2.3 Sulfuric acid (1 1).

5.2.4 Hydrogen peroxide (1 9).

5.2.5 Mixed acid. add 160mL sulfuric acid (11) and 340mL nitric acid (rho=1.42g/mL) to 500mL water.

5.2.6 Titanium standard solution B. Weigh 0.1000g metallic titanium (wTi>=99.9%) into a 300mL beaker, add 50mL sulfuric acid (5.2.3) And 10mL of hydrochloric acid (1 1) after heating to decompose, then add 1mL of nitric acid (5.2.2), heating until the titanium is completely dissolved, and continue to heat to evaporate Remove the white smoke, cool it, carefully add about 10mL of water, dissolve the soluble salts, cool to room temperature, transfer it to a 1000mL volumetric flask, and add water Dilute to the mark and mix well. 1mL of this solution contains 0.1mg of titanium.

5.3 Apparatus

Spectrophotometer.

5.4 Sample

Process the sample into chips with a thickness not exceeding 1 mm.

5.5 Analysis steps

5.5.1 Sample

According to Table 4, weigh the corresponding mass (m2) of the 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 Determination

5.5.3.1 Place the sample (5.5.1) in a 300mL beaker, cover with a watch glass, add 10mL sodium hydroxide solution (5.2.1), wait for a violent reaction After stopping, heat to completely dissolve. After cooling, rinse the watch glass and the wall of the cup with a small amount of water, add 50mL mixed acid (5.2.5) while stirring, add Heat to dissolve salts, boil to drive off nitrogen oxides, and cool to room temperature. Transfer to a.200mL volumetric flask, dilute to the mark with water, and mix.

5.5.3.2 Pipette two portions of test solution (5.5.3.1) according to Table 4, put them in a 50mL volumetric flask, add 15mL mixed acid (5.2.5), one of them Add 5 mL of hydrogen peroxide (5.2.4) in one portion, and no hydrogen peroxide (5.2.4) in the other portion. This solution is a compensation solution; dilute to the mark with water and mix. uniform. Take water as a reference, use an absorption cell of appropriate specifications, measure the absorbance at 410.0nm in a spectrophotometer, and subtract the absorbance of the compensation solution Afterwards, check the corresponding amount of titanium (m3) from the working curve.

5.5.4 Drawing of working curve

Pipette 0mL, 1.00mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL, 10.00mL, 12.00mL titanium standard solution B (5.2.6), put them in 8 50mL volumetric flasks, respectively add 15mL mixed acid (5.2.5), 5mL hydrogen peroxide (5.2.4), and water Dilute to the mark and mix well. Pipette a series of standard solutions into the absorption cell, and measure it at the wavelength of 410.0nm in the spectrophotometer, using water as the reference. Absorbance. Use the amount of titanium as the abscissa and subtract the absorbance of the reagent blank solution as the ordinate to draw a working curve.

5.6 Test data processing

The titanium content is calculated as the mass fraction wTi of titanium and calculated according to formula (2).

5.7 Precision

5.7.1 Repeatability

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

5.7.2 Reproducibility

The measured values of two independent test results obtained under reproducibility conditions are within the average range given below. 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 6. Obtained by interpolation or extension.