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GB/T 6730.6-2016 English PDF (GBT6730.6-2016)

GB/T 6730.6-2016 English PDF (GBT6730.6-2016)

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GB/T 6730.6-2016: Iron ores -- Determination of metallic iron content -- Ferric chloride-sodium acetate titrimetric method

This Part of GB/T 6730 specifies the ferric chloride-sodium acetate titrimetric method to determine the metallic iron content. This Part is applicable to determination of metallic iron content in iron ore, iron concentrate, sinter and pellets. The determination range (mass fraction): 0.150%~3.00%.
GB/T 6730.6-2016
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 73.060.10
D 31
Replacing GB/T 6730.6-1986
Iron ores - Determination of metallic iron content -
Ferric chloride-sodium acetate titrimetric method
ISSUED ON: OCTOBER 13, 2016
IMPLEMENTED ON: SEPTEMBER 01, 2017
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Principle ... 6
4 Reagents ... 6
5 Instruments ... 7
6 Sampling and sample preparation ... 7
7 Analysis steps ... 8
8 Analysis results and their representation ... 10
9 Test report ... 12
Annex A (Normative) Acceptance procedure for specimen analysis results ... 13 Annex B (Informative) Precision test raw data ... 14
Annex C (Informative) Graphical representation of precision results ... 15 Iron ores - Determination of metallic iron content -
Ferric chloride-sodium acetate titrimetric method
WARNING - Persons using this Part shall have experience in formal
laboratory work. This Part does not address all security issues. It is the user's responsibility to take appropriate safety and health measures and to ensure compliance with the conditions stipulated by relevant national regulations.
1 Scope
This Part of GB/T 6730 specifies the ferric chloride-sodium acetate titrimetric method to determine the metallic iron content.
This Part is applicable to determination of metallic iron content in iron ore, iron concentrate, sinter and pellets. The determination range (mass fraction): 0.150%~3.00%.
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 6379.1, Accuracy (trueness and precision) of measurement methods
and results - Part 1: General principles and definitions
GB/T 6379.2, Measurement methods and results - Accuracy (trueness and
precision) - Part 2: Determine the standard methods of measurement
repeatability and reproducibility of the basic method
GB/T 6682, Water for analytical laboratory use - Specification and test methods
GB/T 6730.1, Iron ores - Preparation of pre-dried test samples for chemical analysis
GB/T 6730.3, Iron ores - Determination of hygroscopic moisture in analytical samples - Gravimetric, Karl Fischer and mass-loss methods
GB/T 8170, Rules of rounding off for numerical values and expression and judgement of limiting values
GB/T 10322.1, Iron ores - Sampling and sample preparation procedures
GB/T 12805, Laboratory glassware - Burettes
GB/T 12806, Laboratory glassware - One-mark volumetric flasks
GB/T 12808, Laboratory glassware - One-mark pipettes
3 Principle
The specimen is first separated from non-magnetic substances by magnetic separation. Under electromagnetic stirring conditions, use ferric chloride- sodium acetate buffer solution (pH 2.2~2.4) to selectively dissolve metallic iron. After separation by filtration, use potassium dichromate standard titration solution titrate the filtrate. Other reduced substances and oxidized substances such as high-valent manganese interfere with this method. Calculate the content of metallic iron according to the consumption of potassium dichromate standard titration solution.
4 Reagents
Unless otherwise specified, in the analysis, it shall only use the confirmed analytically-pure reagents and grade three and above distilled water specified in GB/T 6682 or deionized water or equivalent-pure water.
4.1 Anhydrous ethanol.
4.2 Mixed sulfuric acid: 2+3+5.
Pour 300mL of phosphoric acid (??=1.70g/mL) into 500mL of water under stirring. Then slowly add 200mL of sulfuric acid (??=1.84g/mL). Mix well.
4.3 Ferric chloride solution: 30g/L.
Weigh 30g of ferric chloride (FeCl3?€?6H2O) and dissolve in 1000mL of water. Mix well (if the solution is cloudy, it shall be used after filtering).
4.4 Ferric chloride-sodium acetate solution: pH is 2.2~2.4.
Take 100mL of ferric chloride solution (see 4.3) and add 3g of sodium acetate (NaAc?€?3H2O). Mix well. Use pH meter to measure its pH value. If the pH value is unsatisfactory, add ferric chloride solution (see 4.3) or sodium acetate (NaAc ?€?3H2O) to adjust. Prepare it when it is required.
4.5 Potassium dichromate standard titration solution: c(1/6K2Cr2O7) =
0.02000mol/L.
Weigh 0.9806g of potassium dichromate (standard reagent) that is pre-dried at 150??C for 1h and dissolve in water. Transfer to a 1000mL volumetric flask. Use water to dilute to the scale. Mix well.
4.6 Ferrous ammonium sulfate solution: about 0.01mol/L.
Weigh 7.88g of ferrous ammonium sulfate [(NH4)2Fe(SO4)2??6H2O] and dissolve in sulfuric acid (5+95). Transfer to a 2000mL volumetric flask. Use sulfuric acid (5+95) to dilute to the scale. Mix well.
4.7 Sodium diphenylamine sulfonate indicator solution: 2g/L.
Weigh 0.1g of sodium diphenylamine sulfonate and dissolve it in 50mL of water. Add 2 to 3 drops of concentrated sulfuric acid (??=1.84g/mL). Use after the solution is clear.
4.8 Pickled asbestos: Take 10g of pickled asbestos and burn at 900??C for more than 2h in advance. Leave it for future use.
5 Instruments
In the analysis, only common laboratory instruments are used. The burettes, single-marked volumetric flasks and single-marked pipettes used shall comply with the provisions of GB/T 12805, GB/T 12806 and GB/T 12808, respectively. 5.1 Glass petri dish: 9cm~12cm in diameter.
5.2 Ferrite magnet: the magnetic field strength is 1000Oe.
5.3 Non-magnetic metal iron core stirrer.
5.4 Adjustable speed magnetic stirrer.
6 Sampling and sample preparation
6.1 Laboratory specimen
Laboratory specimens for analysis shall be sampled and prepared in
accordance with GB/T 10322.1. The particle size shall be less than 100??m. If the content of combined water or easily oxidized in the specimen is high, the particle size shall be less than 160??m.
NOTE: See GB/T 6730.1 for regulations on high content of combined water and easy oxides.
7.5.1 Decomposition of test material
Place the test material (see 7.2) in a dry Petri dish (see 5.1). Add 15mL~20mL of ethanol (see 4.1). Mix well. Place one end of the ferrite magnet (see 5.2) with a field strength of 1000Oe in a clean small beaker (the diameter of the small beaker is slightly larger than that of the magnet). Use a small beaker to gently grind the test material in a petri dish several times. Lightly lift the small beaker. Rinse off non-magnetic substances with a narrow neck wash bottle filled with ethanol. Move the small beaker over the second clean Petri dish. Take out the magnet. Use a washing bottle to flush the magnetic substance attached to the wall of the small beaker into this Petri dish. Repeat the above magnetic separation action more than 5 times. Transfer all the magnetic material to the second Petri dish.
Add 15mL~20mL of ethanol to the second Petri dish. Magnetic separation in this petri dish. Repeat the above magnetic separation steps for more than 3 times until no magnetic substances are adsorbed in the petri dish. Wash the final selected magnetic substance into a 250mL beaker. After attaching the magnet to the bottom of the beaker to attract the magnetic substance, slowly pour out a small amount of non-magnetic substances and ethanol brought in by inclusions. Pour out as much ethanol as possible. (If it is difficult to separate non-magnetic minerals, the test material in the second petri dish can be washed into another petri dish first. Repeat the above magnetic separation steps and then magnetic separation more than 3 times to wash into the beaker.)
Add 30mL of ferric chloride-sodium acetate solution (see 4.4). Put in a non- magnetic metal iron core stirrer (see 5.3). Cover the watch glass. Put on a magnetic stirrer (see 5.4) and stir for 40min at a speed of 200r/min. Use medium-speed qualitative filter paper (add appropriate amount of pulp) or acid- washed asbestos (see 4.8) to filter. Use water to wash the beaker 3~4 times. Wash the residue 6 to 8 times.
NOTE: During filtration, a flat magnet block can be used to absorb the magnetic minerals at the bottom of the conical flask. Make it as little as possible into the filter paper. Pour filtering, so as to speed up the filtration rate.
7.5.2 Determination of test material
Add 20 mL of thiophosphoric acid (see 4.2) to the filtrate (see 7.5.1). The control volume is 120mL~150mL. Let stand until the yellow color subsides slightly. Add 5 drops of sodium diphenylamine sulfonate indicator solution (see 4.7). Use potassium dichromate standard titration solution (see 4.5) to titrate to a stable purple color.
7.5.3 Determination of blank value
Add 10.00mL of ferrous ammonium sulfate solution (see 4.6) and 20mL of
(CRM) or reference materials (RM). Final laboratory results are used for comparison with CRM or RM standard value Ac. Two possibilities will arise: a) , in this case, there is no significant difference
between the measured value and the standard value;
b) , in this case, there is a significant difference between
the measured value and the standard value.
Where,
??c - The measured value of CRM or RM;
Ac - The standard value of CRM or RM.
8.2.5 Calculation of final result
The final result is the arithmetic mean of the acceptable values for the specimen, or the value determined by the procedure specified in Annex A. The analysis result is rounded up according to the provisions of GB/T 8170. When the analysis result is less than 1.00%, round the value to three decimal places. When the analysis result is equal to or greater than 1.00%, round the value to two decimal places.
9 Test report
The test report shall contain the following information:
a) Laboratory name and address;
b) Test report release date;
c) Reference to this Part;
d) Detailed instructions necessary for specimen identification;
e) Analysis results;
f) Number of determination of results;
g) Any abnormal characteristics present in the determination process and any operations not specified in the standard that may affect the analytical results of the specimen or certified standard sample.

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