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GB/T 8704.5-2020: Ferrovanadium - Determination of vanadium content - The ammonium ferrous sulfate titrimetric method and the potentiometric titrimetric method Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB/T 8704.5: Historical versions
Similar standardsGB/T 8704.5-2020: Ferrovanadium - Determination of vanadium content - The ammonium ferrous sulfate titrimetric method and the potentiometric titrimetric method---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT8704.5-2020 GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 77.100 H 11 Replacing GB/T 8704.5-2007 Ferrovanadium - Determination of vanadium content - The ammonium ferrous sulfate titrimetric method and the potentiometric titrimetric method ISSUED ON: JUNE 02, 2020 IMPLEMENTED ON: SEPTEMBER 01, 2020 Issued by: State Administration for Market Regulation; Standardization Administration of the People's Republic of China. Table of ContentsForeword ... 3 1 Scope ... 5 2 Normative references ... 5 3 Method One - Visual titration method ... 6 4 Method Two: Potentiometric titration method ... 11 5 Test report ... 15 Annex A (normative) Flowchart of procedures for accepting analysis values of test sample ... 16 Annex B (informative) Raw data of precision test ... 18 Ferrovanadium - Determination of vanadium content - The ammonium ferrous sulfate titrimetric method and the potentiometric titrimetric method WARNING - Personnel using this Part shall have practical experience in formal laboratory work. This Part does not point out all possible safety issues. 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 8704 specifies to use the ammonium ferrous sulfate titrimetric method and the potentiometric titrimetric method to determine vanadium content. This Part is applicable to the determination of vanadium content in ferrovanadium. The determination range (mass fraction) is: 35.00%~85.00%.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 4010, Ferroalloys sampling and preparation of samples for chemical analysis GB/T 6379.1, Accuracy (trueness and precision) of measurement methods and results - Part 1: General principles and definitions GB/T 6379.2, Accuracy (trueness and precision) of measurement methods and results - Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method GB/T 6682, Water for analytical laboratory use - Specification and test methods GB/T 8170, Rules of rounding off for numerical values & expression and 3.2.9 Sodium nitrite solution, 20g/L. 3.2.10 Manganese sulfate solution, 10g/L. 3.2.11 Potassium dichromate standard solution, c(1/6K2Cr2O7) = 0.07000mol/L. Weigh 3.4322g of benchmark potassium dichromate that has been dried in an electric oven at 120°C to constant weight. Place in a 300mL beaker. Use water to dissolve. Move into a 1000mL volumetric flask. Use water to dilute to the scale. Mix well. 3.2.12 Ferrous ammonium sulfate standard solution (about 0.07mol/L) 3.2.12.1 Preparation Weigh 27.45g of ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] in a 300mL beaker. Dissolve in appropriate amount of sulfuric acid (5+95). Use sulfuric acid (5+95) to dilute to 1000mL. Mix well. 3.2.12.2 Calibration and indicator calibration Dispense 5.00mL of potassium dichromate standard solution (see 3.2.11) into three portions. Respectively place in 500mL Erlenmeyer flasks. Successively add 20mL of sulfuric acid (see 3.2.5), 5mL of phosphoric acid (see 3.2.3), 70mL of water, 3 drops of N-phenylanthranilic acid indicator solution (see 3.2.14). Use ferrous ammonium sulfate standard solution (see 3.2.12) to titrate the solution from purple-red to bright yellow-green as the end point. The volume of ferrous ammonium sulfate standard titration solution is not counted. Add 20.00mL (V01) of potassium dichromate standard solution (see 3.2.11). Use ferrous ammonium sulfate standard titration solution (see 3.2.12) to titrate the solution from purple-red to bright yellow-green as the end point. Record the consumed volume of ferrous ammonium sulfate standard titration solution V1. The difference in the volume of ferrous ammonium sulfate standard titration solution consumed by three potions of potassium dichromate standard solutions does not exceed 0.05mL. Take the average. Calculate the concentration of ferrous ammonium sulfate standard titration solution according to formula (1): Where, c1 - Concentration of ferrous ammonium sulfate standard titration solution, in Mole per liter (mol/L); b) Ammonium persulfate oxidation In the test solution (see 3.5.5.1), add 4g~5g of ammonium persulfate (see 3.2.1). Add 5mL of manganese sulfate solution (see 3.2.10). Mix well. Heat and boil until big bubbles appear. Remove. Use a little water to rinse the bottle wall. Boil for another 2min~3min. Remove and cool to room temperature. 3.5.5.3 Titration In the test solution (see 3.5.5.2), add 3 drops of N-phenylanthranilic acid indicator solution (see 3.2.14). Immediately use ferrous ammonium sulfate standard titration solution (see 3.2.12) to titrate the solution from purple-red to bright yellow-green as the end point. The volume of the consumed ferrous ammonium sulfate standard titration solution is V4. 3.6 Calculation and expression of analysis result 3.6.1 Calculation of vanadium content Calculate vanadium content wv according to formula (2), in mass fraction (%): Where, c1 - Concentration of ferrous ammonium sulfate standard titration solution, in Mole per liter (mol/L); V4 - Volume of ferrous ammonium sulfate standard titration solution consumed to titrate the test material solution, in milliliters (mL); V0 - Volume of ferrous ammonium sulfate standard titration solution consumed to titrate the blank test solution, in milliliters (mL); 50.94 - Molar mass of vanadium, in grams per mole (g/mol); m - Amount of test material, in grams (g). 3.6.2 Determination and expression of analysis results If the absolute value of the difference between two independent analysis results of the same sample is not greater than the repeatability limit r, then take the arithmetic mean as the analysis result. If the absolute value of the difference between the two independent analysis results is greater than the repeatability limit r, then increase the number of determinations and determine the analysis 4.2.3 Phosphoric acid, ρl.70g/mL. 4.2.4 Sulfuric acid, 1+1. 4.2.5 Sodium nitrite solution, 10g/L. 4.2.6 Potassium permanganate solution, 6.3g/L. 4.2.7 Potassium dichromate standard solution, c(1/6K2Cr2O7) = 0.2000mol/L. Precisely weigh 9.8064g of benchmark potassium dichromate that has been pre-dried at 150°C for 2h and cooled to room temperature in a dryer. Place in a 300mL beaker. Use water to completely dissolve. Move into a 1000mL volumetric flask. Use water to dilute to the scale. Mix well. 4.2.8 Ferrous ammonium sulfate standard titration solution c [(NH4)2Fe(SO4)2·6H2O] = 0.2mol/L. 4.2.8.1 Preparation Weigh 78.4g of ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] in a 500mL beaker. Use an appropriate amount of sulfuric acid (5+95) to completely dissolve. Move into a 1000mL volumetric flask. Use sulfuric acid (5+95) to dilute to the scale. Mix well. 4.2.8.2 Calibration In a 600mL beaker that is filled with 270mL of water, 10mL of phosphoric acid (see 4.2.3) and 20mL of sulfuric acid (see 4.2.4), use a burette to add 40.00mL of potassium dichromate standard solution (see 4.2.7). Use ferrous ammonium sulfate standard titration solution (see 4.2.8) to conduct potentiometric titration. Under the potentiometer check, use ferrous ammonium sulfate standard titration solution (see 4.2.8) to slowly titrate to the end point. Continue to add 0.05mL each time or add drop by drop. Record the potential reading and titration volume every time the potential is balanced. Continue to drip till it exceeds the end point. Determine the end point from potentiometric titration curve or dE/dV curve. Record the volume of ferrous sulfate standard solution consumed at the end of the titration, V5. Calculate the concentration of ferrous ammonium sulfate standard titration solution (4.2.8) according to formula (3): Where, c2 - Concentration of ferrous ammonium sulfate standard titration solution, in Mole per liter (mol/L); c02 - Concentration of potassium dichromate standard solution, in Mole per liter (mol/L); V02 - Volume of potassium dichromate standard solution, in milliliters (mL); V5 - Volume of ferrous ammonium sulfate standard titration solution consumed when calibrating, in milliliters (mL). 4.3 Instruments 4.3.1 Magnetic stirrer. 4.3.2 Automatic potentiometric titrator, equipped with platinum electrode and calomel electrode. 4.4 Sample extraction and preparation Extract and prepare samples according to GB/T 4010. All samples shall pass through the 0.180mm sieve. 4.5 Analysis steps 4.5.1 Number of determinations For the same sample, at least independently determine twice. 4.5.2 Test material Weigh 0.50g of test material, to the nearest of 0.0001g. 4.5.3 Blank test Conduct the blank test with test material. The reagents used shall be taken from the same reagent bottle. 4.5.4 Verification test Analyze the same type of standard sample along with test material. 4.5.5 Determination 4.5.5.1 Place the test material (see 4.5.2) in a 400mL beaker. Add 10mL of water, 10mL of nitric acid (see 4.2.2), 50mL of sulfuric acid (see 4.2.4). Heat till all the test material is dissolved. Evaporate to emit sulfuric acid white smoke. Remove and cool. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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