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Delivery: <= 3 days. True-PDF full-copy in English will be manually translated and delivered via email. GB/T 20975.16-2020: Methods for chemical analysis of aluminium and aluminium alloys - Part 16: Determination of magnesium content Status: Valid GB/T 20975.16: Historical versions
Basic dataStandard ID: GB/T 20975.16-2020 (GB/T20975.16-2020)Description (Translated English): Methods for chemical analysis of aluminium and aluminium alloys - Part 16: Determination of magnesium content Sector / Industry: National Standard (Recommended) Classification of Chinese Standard: H12 Classification of International Standard: 77.120.10 Word Count Estimation: 14,175 Date of Issue: 2020-06-02 Date of Implementation: 2021-04-01 Older Standard (superseded by this standard): GB/T 20975.16-2008 Quoted Standard: GB/T 8005.2; GB/T 8170-2008 Issuing agency(ies): State Administration for Market Regulation, China National Standardization Administration Summary: This standard specifies the determination of magnesium content in aluminum and aluminum alloys by CDTA titration, flame atomic absorption spectrometry and Na?EDTA titration. This standard applies to the arbitration determination of magnesium content in aluminum and aluminum alloys. Determination range of CDTA titration: 0.10%��12.00%; Determination range of flame atomic absorption spectrometry: 0.002 0%��5.00%; Determination range of Na?EDTA titration: 1.00%��52.00%. GB/T 20975.16-2020: Methods for chemical analysis of aluminium and aluminium alloys - Part 16: Determination of magnesium content---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order. Methods for chemical analysis of aluminium and aluminium alloys--Part 16.Determination of magnesium content ICS 77.120.10 H12 National Standards of People's Republic of China Replace GB/T 20975.16-2008 Chemical analysis methods of aluminum and aluminum alloys Part 16.Determination of Magnesium Content 2020-06-02 released Implementation on 2021-04-01 State Administration for Market Regulation Issued by the National Standardization Management Committee ForewordGB/T 20975 "Methods for Chemical Analysis of Aluminum and Aluminum Alloys" is divided into 37 parts. ---Part 1.Determination of mercury content; ---Part 2.Determination of arsenic content; ---Part 3.Determination of copper content; ---Part 4.Determination of iron content ---Part 5.Determination of silicon content; ---Part 6.Determination of cadmium content; ---Part 7.Determination of manganese content; ---Part 8.Determination of zinc content; ---Part 9.Determination of lithium content by flame atomic absorption spectrometry; ---Part 10.Determination of tin content; ---Part 11.Determination of lead content; ---Part 12.Determination of titanium content; ---Part 13.Determination of vanadium content; ---Part 14.Determination of nickel content; ---Part 15.Determination of boron content; ---Part 16.Determination of magnesium content; ---Part 17.Determination of strontium content; ---Part 18.Determination of chromium content; ---Part 19.Determination of Zirconium Content; ---Part 20.Determination of Gallium Content Butyl Rhodamine B Spectrophotometry; ---Part 21.Determination of calcium content; ---Part 22.Determination of beryllium content; ---Part 23.Determination of antimony content; ---Part 24.Determination of total rare earth content; ---Part 25.Determination of element content by inductively coupled plasma atomic emission spectrometry; ---Part 26.Determination of carbon content by infrared absorption method; ---Part 27.Determination of cerium, lanthanum and scandium content by inductively coupled plasma atomic emission spectrometry; ---Part 28.Determination of cobalt content by flame atomic absorption spectrometry; ---Part 29.Determination of molybdenum content thiocyanate spectrophotometric method; ---Part 30.Determination of hydrogen content by heating extraction thermal conductivity method; ---Part 31.Determination of phosphorus content molybdenum blue spectrophotometric method; ---Part 32.Determination of Bismuth Content; ---Part 33.Determination of potassium content by flame atomic absorption spectrometry; ---Part 34.Determination of sodium content by flame atomic absorption spectrometry; ---Part 35.Determination of Tungsten Content Thiocyanate Spectrophotometric Method; ---Part 36.Determination of silver content by flame atomic absorption spectrometry; --- Part 37.Determination of Niobium Content. This part is Part 16 of GB/T 20975. This section was drafted in accordance with the rules given in GB/T 1.1-2009. This section replaces GB/T 20975.16-2008 "Methods for Chemical Analysis of Aluminum and Aluminum Alloys Part 16.Determination of Magnesium Content". Headquarters Compared with GB/T 20975.16-2008, the main technical changes except for editorial changes are as follows. --- Added standard use safety warnings; ---Modified the sample size in "CDTA Titration Method" (see Table 1,.2008 version 6.1); --- Added "Normative Reference Documents" (see Chapter 2); --- Added "Terms and Definitions" (see Chapter 3); ---Modified the repeatability limit of "CDTA Titration Method" (see 4.7.1, 8.1 in.2008 edition); ---Modified the method summary of "Flame Atomic Absorption Spectrometry" (see 5.1, Chapter 10 of the.2008 edition); --- Modify the precision of "Flame Atomic Absorption Spectrometry" (see Chapter 5.7, Chapter 17 of the.2008 edition); ---Added "Na2EDTA Titration" (see Chapter 6); --- Deleted "quality control and assurance" (see Chapter 18 of the.2008 edition); --- Added "Test Report" (see Chapter 7). This part was proposed by China Nonferrous Metals Industry Association. This part is under the jurisdiction of the National Nonferrous Metals Standardization Technical Committee (SAC/TC243). Drafting organizations of this section. Northeast Light Alloy Co., Ltd., National Standard (Beijing) Inspection and Certification Co., Ltd., Non-ferrous Metal Technology and Economic Research Institute Research Institute, Shandong Nanshan Aluminum Co., Ltd., Hebei Sitong New Metal Materials Co., Ltd., Chinalco Ruimin Co., Ltd., Guangxi Liuzhou Yinhai Aluminum Co., Ltd., Youyan Yijin New Material Co., Ltd., Shandong Yankuang Light Alloy Co., Ltd., Changsha Research Institute of Mining and Metallurgy have Limited Liability Company, Guizhou Institute of Analysis and Testing, Kunming Metallurgical Research Institute, and Standard Technical Service (Tianjin) Co., Ltd. The main drafters of this section. Zhao Shizhuo, Zhang Xu, Xi Huan, Cong Fuguan, Tian Xin, Zhao Zhiguo, Lan Zheng, Li Tian, Xu Tao, Gao Jun, Luo Fen, Pang Xin, Lou Yue, Tang Weiju, Zhou Ting, Yuan Xiao, Li Yue, Li Yanzhen, Zhou Bing. The previous versions of the standards replaced by this part are as follows. ---GB/T 6987.16-1986, GB/T 6987.16-2001; ---GB/T 6987.17-1986, GB/T 6987.17-2001; ---GB/T 20975.16-2008. Chemical analysis methods of aluminum and aluminum alloys Part 16.Determination of Magnesium Content Warning---Personnel using this section should have practical experience in formal laboratory work. This section does not point out all possible safety issues question. The user is responsible for taking appropriate safety and health measures and ensuring compliance with the conditions stipulated by relevant national laws and regulations.1 ScopeThis part of GB/T 20975 specifies the CDTA titration, flame atomic absorption spectrometry and Na2EDTA titration for the determination of aluminum and Magnesium content in aluminum alloy. This section applies to the arbitration determination of magnesium content in aluminum and aluminum alloys. CDTA titration measurement range. 0.10%~12.00%; flame Atomic absorption spectrometry measurement range. 0.0020%~5.00%; Na2EDTA titration measurement range. 1.00%~52.00%. Note. When the mass fraction of magnesium is >0.10%~5.00%, flame atomic absorption spectrometry is used as the arbitration method; when the mass fraction of magnesium is >5.00%~12.00%, it is used The Na2EDTA titration method is the arbitration method.2 Normative referencesThe following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this article Pieces. For undated references, the latest version (including all amendments) applies to this document. GB/T 8005.2 Terminology of Aluminum and Aluminum Alloy Part 2.Chemical Analysis GB/T 8170-2008 Numerical rounding rules and the expression and determination of limit values3 Terms and definitionsThe terms and definitions defined in GB/T 8005.2 apply to this document.4 CDTA titration4.1 Method summary The sample was dissolved in hydrochloric acid, and the magnesium in the residue was recovered by filtration. Precipitating magnesium with sodium hydroxide in the presence of hydrogen peroxide, potassium cyanide and a small amount of iron And separated from a large amount of aluminum, zinc, copper, nickel and chromium. Dissolve the precipitate with hydrochloric acid, in the presence of potassium permanganate, separate a small amount of iron, manganese, Aluminum and titanium. The sample solution uses methyl thymol blue as the indicator, and titrates with the CDTA standard titration solution until the solution changes from blue to light gray Color is the end point to determine the magnesium 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 Zinc oxide. 4.2.2 Bromine water (saturated solution). 4.2.3 Hydrofluoric acid (ρ=1.14g/mL). 4.2.4 Hydrogen peroxide (ρ=1.10g/mL). 4.2.5 Ammonia (ρ=0.90g/mL). 4.2.6 Hydrochloric acid (about 0.05mol/L). 4.2.7 Hydrochloric acid (11). 4.2.8 Ammonia (11). 4.2.9 Nitric acid (2 3). 4.2.10 Sulfuric acid (1 3). 4.2.11 Ethanol (1 3). 4.2.12 Hydrochloric acid (1 5). 4.2.13 Ammonia (1 13). 4.2.14 Potassium cyanide solution (250g/L). Equipped when used. Very toxic, pay attention when using 4.2.15 Sodium hydroxide solution (240g/L). Store in plastic bottles. 4.2.16 Sodium hydroxide solution (20g/L). Store in plastic bottles. 4.2.17 Hydroxylamine hydrochloride solution (18g/L). 4.2.18 Potassium permanganate solution (10g/L). 4.2.19 Ferric chloride solution (1mg/mL). Weigh 0.48g ferric chloride (FeCl3 6H2O) and dissolve it in 16mL hydrochloric acid (4.2.12), Transfer to a 100mL volumetric flask, dilute to the mark with water, and mix. This solution 1mL contains 1mg iron. 4.2.20 Ethylene glycol-bis(2-aminoethyl ether)tetraacetic acid (EGTA) solution (0.05mol/L). Weigh 1.9g EGTA and dissolve it in 25mL hydrogen Sodium oxide solution (4.2.16), transfer to a 100mL volumetric flask, dilute to the mark with water, and mix. 4.2.21 Magnesium standard solution A (ρ2=1mg/mL). Use a certified standard solution to prepare. Or weigh 1.0000g magnesium (wMg≥ 99.95%) placed in a 500mL beaker, add.200mL water, add 30mL hydrochloric acid (4.2.7) in total in batches, and after it is completely dissolved, transfer Put it into a 1000mL volumetric flask, dilute to the mark with water, and mix well. 1mL of this solution contains 1mg of magnesium. 4.2.22 Magnesium standard solution B (ρ4=0.2mg/mL). Pipette 100.0mL magnesium standard solution A (4.2.21) into a 500mL volumetric flask, Add 6mL hydrochloric acid (4.2.7), dilute to the mark with water, and mix. 1mL of this solution contains 0.2mg of magnesium. 4.2.23 1,2-cyclohexanediaminetetraacetic acid (CDTA) standard titration solution A (c1≈0.035mol/L). ---Preparation. Weigh 12.75g CDTA into a 1000mL beaker, add about 500mL water, add 10mL sodium hydroxide to dissolve Liquid (4.2.15), stir for a few minutes. Add 10mL~15mL sodium hydroxide solution (4.2.15) to completely dissolve. Use slow Quantitative filter paper is filtered in a 1000mL volumetric flask, washed with water and diluted to the mark, and mixed. Store in a polyethylene bottle. ---Calibration. Pipette 3 volumes (V2) of 25.00mL magnesium standard solution A (4.2.21) into a 500mL conical beaker, and add 5g ammonium chloride, diluted with water to about 100mL, add 100mL ammonia water (4.2.5), cool, add 0.05g~0.1g methyl musk Vanillol blue indicator (4.2.25), titrated with CDTA standard titration solution A (4.2.23) until the solution changes from blue to light gray, The color of the excess 2 drops does not change to the end point. The volume of CDTA standard titration solution (4.2.23) consumed for parallel calibration should not More than 0.15mL, take the average value (V1). ---Calculation. Calculate the concentration of CDTA standard titration solution according to formula (1). c1= ρ 2V2 24.305V1 (1) Where. ρ2 --- The mass concentration of magnesium standard solution A (4.2.21), in milligrams per milliliter (mg/mL); V2 --- The volume of the magnesium standard solution A (4.2.21) to be pipetted, in milliliter (mL); 24.305---The molar mass of magnesium, in grams per mole (g/mol); V1 --- The volume of CDTA standard titration solution A (4.2.23) consumed for calibration, in milliliter (mL). The calculation result retains four significant figures. The rounding of values shall be implemented in 3.2 and 3.3 of GB/T 8170-2008. 4.2.24 1,2-Cyclohexanediaminetetraacetic acid (CDTA) standard titration solution B (c3≈0.01mol/L). ---Preparation. Weigh 3.64g CDTA into a 1000mL beaker, add about 500mL water, and add 5mL sodium hydroxide solution (4.2.15), stir for a few minutes. Add 10mL~15mL sodium hydroxide solution (4.2.15) to completely dissolve. Use slow speed Filter the amount of filter paper in a 1000mL volumetric flask, wash with water and dilute to the mark, and mix. Store in a polyethylene bottle. ---Calibration. Pipette 3 parts (V4) of 30.00mL magnesium standard solution B (4.2.22) into a 500mL conical beaker, and add 5g ammonium chloride, diluted with water to about 100mL, add 100mL ammonia water (4.2.5), cool, add 0.05g~0.1g methyl musk Vanillol blue indicator (4.2.25), titrate with CDTA standard titration solution B (4.2.24) until the solution changes from blue to light gray, The color of the excess 2 drops does not change to the end point. The volume of CDTA standard titration solution (4.2.24) consumed for parallel calibration should not More than 0.10mL, take the average value (V3). ---Calculation. Calculate the concentration of the CDTA standard titration solution according to formula (2). c3= ρ 4V4 24.305V3 (2) Where. ρ4 --- The mass concentration of magnesium standard solution B (4.2.22), in milligrams per milliliter (mg/mL); V4 --- The volume of the magnesium standard solution B (4.2.22) to be pipetted, in milliliter (mL); 24.305---The molar mass of magnesium, in grams per mole (g/mol); V3 --- The volume of CDTA standard titration solution B (4.2.24) consumed during calibration, in milliliters (mL). The calculation result retains four significant figures. The rounding of values shall be implemented in 3.2 and 3.3 of GB/T 8170-2008. 4.2.25 Methyl thymol blue indicator. Weigh 0.1g of methyl thymol blue and 10g of sodium chloride, grind and mix. 4.3 Apparatus PH 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 According to Table 1, weigh the sample (4.4) of the corresponding mass (m1) to the nearest 0.0001g. 4.5.2 Parallel experiment Do two tests in parallel and take the average value. 4.5.3 Blank test Do a reagent blank test with the sample (4.5.1). Record the volume of CDTA standard solution (V5) consumed during the titration of the blank solution. 4.5.4 Determination 4.5.4.1 Put the sample (4.5.1) in a 400mL beaker, cover with a watch glass, add water and hydrochloric acid (4.2.7) according to Table 1, and wait until the violent reaction stops After that, add 10mL nitric acid (4.2.9), slowly heat until the sample is completely dissolved, and boil for 10min. Wash watch dishes and cup walls with hot water and dilute the body It is accumulated to 150mL~200mL, filter with a slow quantitative filter paper, wash the filter paper and residue with hot hydrochloric acid (4.2.6) 8 to 10 times, and collect the filtrate And washing liquid in a 400mL beaker. If there is a large amount of residue, put the filter paper together with the residue in a platinum crucible, dry and ash at 550℃. Whole (don't burn the filter paper), let cool. Add 2mL sulfuric acid (4.2.10), 5mL hydrofluoric acid (4.2.3), add nitric acid (4.2.9) dropwise to the solution Clear. Heat and evaporate until the sulfuric acid fumes are removed, and burn for 10min (≤700℃). cool down. Add 5mL water and 2mL hydrochloric acid (4.2.7), add Heat to completely dissolve the precipitate (if turbidity needs to be filtered), combine this solution with the main sample solution. Concentrate the volume to about 100 mL. Table 1 Magnesium mass fraction wMg/% sample mass m1/g water/mL hydrochloric acid/mL 0.10~0.50 2.00 30 50 >0.50~2.00 1.00 20 30 >2.00~7.00 0.50 10 20 >7.00~12.00 0.25 5 15 4.5.4.2 Add 5 mL of ferric chloride solution (4.2.19) to the sample solution (4.5.4.1), and transfer the sample solution into the pre-filled 70 mL hydrogen Sodium oxide solution (4.2.15) in a 400mL beaker, mix well. Add 2mL hydrogen peroxide (4.2.4), boil for 5min~10min. take under. Add 5mL potassium cyanide solution (4.2.14), boil for 5min. Dilute the volume with hot water to approximately 250 mL. Cover the watch glass to keep warm (but Do not boil) not less than 20min. Filter with slow quantitative filter paper, wash the precipitate and filter paper 5 times with hot sodium hydroxide solution (4.2.16). Keep Beaker. Dispose of the filtrate after harmless treatment. 4.5.4.3 Dissolve the precipitate in the original beaker with a mixture of 50 mL of hot hydrochloric acid (4.2.12) and 2 mL of hydroxylamine hydrochloride solution (4.2.17). Wash the filter paper thoroughly with water, keep the volume less than 70 mL, and heat until the sample solution is clear. Drop bromine water (4.2.2) until the color of bromine remains unchanged And excess 3mL, boil to remove excess bromine, dilute with water to a volume of about 80mL, and cool. 4.5.4.4 Adjust the sample solution to pH 4 with ammonia water (4.2.8), then adjust the sample solution to pH (4.4 ± 0.2) with ammonia water (4.2.13), and heat to boiling, Add 0.3g zinc oxide (4.2.1) (first make a paste with water and then move it into the sample solution), shake well. Add potassium permanganate solution (4.2.18) dropwise to stable Set the khaki, heat to boiling. Remove, add 2mL ethanol (4.2.11), shake well. Place it on a boiling water bath and heat for 5 min, add 2 mL of ethyl acetate Alcohol (4.2.11), mix well. Place on a boiling water bath and continue heating for 10 minutes. Filter the sample solution on a 500mL cone with slow quantitative filter paper In the cup, wash the sediment and filter paper 8 times with hot water and cool. 4.5.4.5 Adjust to slightly alkaline with ammonia (4.2.5) (check with test paper). If the sample solution is colorless, add 8mL potassium cyanide solution (4.2.14), If the sample solution is blue, add potassium cyanide solution (4.2.14) dropwise while stirring until the sample solution becomes colorless and an excess of 8 mL. Add 1mL EGTA solution (4.2.20), 100mL ammonia (4.2.5), 0.05g~0.1g methyl thymol blue indicator (4.2.25), shake well. 4.5.4.6 When the mass fraction of magnesium is ≤0.50%, use CDTA standard titration solution B (4.2.24); when the mass fraction of magnesium is >0.50%, use CDTA Standard titration solution A (4.2.23); titrate until the sample solution changes from blue to light gray, and the color of the excess 2 drops does not change as the end point. Record consumption CDTA standard titration solution (4.2.24 or 4.2.23) volume (V6). 4.6 Processing of test data The magnesium content is calculated as the magnesium mass fraction wMg, calculated according to formula (3). wMg= c×(V6-V5)×24.305 m1×1000 × 100% (3) Where. c ---The concentration of CDTA standard titration solution (4.2.24 or 4.2.23), in moles per liter (mol/L); V6 --- The volume of the CDTA standard titration solution (4.2.24 or 4.2.23) consumed during titration, in milliliters (mL); V5 --- The volume of the CDTA standard titration solution (4.2.24 or 4.2.23) consumed in the blank test, in milliliter (mL); 24.305---The molar mass of magnesium, in grams per mole (g/moL); m1 --- The mass of the sample, in grams (g). The calculation result is expressed to two decimal places. Numerical rounding is implemented in 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, 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 uses linear interpolation according to the data in Table 2 Method or extension method. Table 2 wMg/% 0.13 1.71 6.62 12.38 r/% 0.01 0.06 0.10 0.18 4.7.2 Toleran...... |
