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GB/T 8704.5-2020 English PDF (GBT8704.5-2020)

GB/T 8704.5-2020 English PDF (GBT8704.5-2020)

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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

This 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%.
GB/T 8704.5-2020
GB
NATIONAL STANDARD OF THE
PEOPLE 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 Contents
Foreword ... 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 Scope
This 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 references
The 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 and 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, ??l.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.

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