GB/T 13747.4-2020Methods for chemical analysis of zirconium and zirconium alloysPart 4: Determination of chromium content - Diphenylcarbazide spectrophotometry and inductively coupled plasma atomic emission spectrometry (English PDF)

2.5 Test procedure

2.5.1 Sample Weigh the sample (2.4) according to Table 1, accurate to 0.0001g.

2.5.2 Parallel test Do two tests in parallel and take the average value.

2.5.3 Blank test Do a blank test with the sample.

2.5.4 Determination

2.5.4.1 Place the sample (2.5.1) in a 150mL beaker, add 6g of ammonium sulfate (2.2.1) and 10mL of sulfuric acid (2.2.2), cover with a watch glass, Heat to complete decomposition, cool to room temperature, add about 30mL of water to dissolve the salts, transfer to a 100mL volumetric flask, dilute to the mark with water, Mix well.

2.5.4.2 When the chromium content is 0.0020%~0.020%, pipette 10.00mL test solution into a 150mL beaker, add 1.0mL sulfuric acid (2.2.3) and 39mL water; when the chromium content is greater than 0.020%~0.20%, pipette 5.00mL test solution into a 150mL beaker, add 2.0mL Sulfuric acid (2.2.3) and 43mL water.

2.5.4.3 Add potassium permanganate solution (2.2.4) dropwise until the solution turns into a stable red and excess 2 to 3 drops, then slowly boil for a few minutes to make the chromium oxide Completely. After cooling to room temperature, add 20 mL of urea solution (2.2.5), shake well, add dropwise sodium nitrite solution (2.2.6) to make potassium permanganate The magenta disappears, shake until the bubbles stop, transfer to a 100mL volumetric flask, cool to room temperature with running water, add 5mL diphenylcarbazide ethanol Solution (2.2.7), dilute to the mark with water, mix well, and place for 5 min.

2.5.4.4 Pipette part of the solution into a 1cm cuvette, use the blank solution with the sample as a reference, and use the spectrophotometer with a wavelength of 540nm At the place, measure its absorbance. Find the corresponding chromium content from the working curve.

2.5.5 Drawing of working curve

2.5.5.1 Pipette 0mL, 0.50mL, 1.00mL, 3.00mL, 5.00mL, 7.00mL, 10.00mL chromium standard solution (2.2.9), Do not place it in a set of 150mL beakers, add 4.0mL sulfuric acid (2.2.3), and dilute with water to about 50mL volume. Follow

2.5.5.2 Pipette part of the solution into a 1cm cuvette, use the reagent blank solution as a reference, and measure at the wavelength of 540nm on the spectrophotometer. Its absorbance. Use chromium content as the abscissa and absorbance as the ordinate to draw a working curve.

2.6 Test data processing The chromium content is calculated as the mass fraction wCr of chromium, calculated according to formula (1).

2.7 Precision

2.7.1 Repeatability The measured values of two independent test results obtained under repeatability conditions are within the range of the average value given in Table 2. The absolute difference does not exceed the repeatability limit (r), and the case of exceeding the repeatability limit (r) does not exceed 5%. Repeatability limit (r) adopts the line according to the data in Table

2 Obtained by sexual interpolation or extension method.

2.7.2 Reproducibility The measured value of the independent test result obtained under the reproducibility condition is within the range of the average value given in Table 3. The difference does not exceed the reproducibility limit (R), and the reproducibility limit (R) does not exceed 5%. Reproducibility limit (R) is linear according to the data in Table 3. Obtained by interpolation or extension.

3.5 Test procedure

3.5.1 Sample Weigh 0.50g sample (3.4), accurate to 0.0001g.

3.5.2 Parallel test Do two tests in parallel and take the average value.

3.5.3 Blank test Weigh the metal zirconium (3.2.4) equivalent to the sample, and do a blank test with the sample.

3.5.4 Preparation of test solution

3.5.4.1 Place the sample (3.5.1) in a.200mL polytetrafluoroethylene beaker, add 10mL hydrochloric acid (3.2.2), 2mL hydrofluoric acid (3.2.3), heating at low temperature until the sample is completely dissolved, add 0.5mL nitric acid (3.2.1). Cool to room temperature.

3.5.4.2 Transfer to a 100mL plastic volumetric flask, dilute to the mark with water, and mix.

3.5.5 Preparation of working curve solution Weigh 6 parts of 0.500g metal zirconium (3.2.4) into a set of.200mL PTFE beakers, dissolve them according to 3.5.4, and cool Then transfer to a set of 100mL plastic volumetric flasks, add 0mL, 0.50mL, 1.00mL, 5.00mL, 10.00mL, 25.00mL in sequence Chromium standard solution (3.2.6), dilute to the mark with water, and mix.

3.5.6 Measurement

3.5.6.1 Recommended analysis line. 267.71nm.

3.5.6.2 On the inductively coupled plasma atomic emission spectrometer, measure the working curve solution (3.5.5) at the selected analysis wavelength, and then When the curve linearity k>=0.999, the test solution (3.5.4) is measured, the background of the element spectrum line is checked and corrected at the appropriate position, and the The computer automatically gives the mass concentration of chromium.

3.6 Test data processing The chromium content is calculated as the mass fraction of chromium wCr, calculated according to formula (2).

3.7 Precision

3.7.1 Repeatability The measured values of two independent test results obtained under repeatability conditions are within the average range given in Table 4, and the 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%. Repeatability limit (r) adopts the line according to the data in Table

4 Obtained by sexual interpolation or extension method.

3.7.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions are within the range of the average value given in Table 5. The absolute difference does not exceed the reproducibility limit (R), and does not exceed 5% in the case of exceeding the reproducibility limit (R). Reproducibility limit (R) is adopted according to the data in Table

5 Obtained by linear interpolation or extension method.