ICS 73.060.10
D 31
National Standard of the People’s Republic of China
GB/T 6730.65-2009
Iron ores - Determination of total iron content - Titanium (III) chloride reduction potassium dichromate titration methods (routine methods)
鐵礦石 全鐵含量的測定
三氯化鈦還原重鉻酸鉀滴定法
（常規方法）
(English Translation)
Issue date: 2009-10-30 Implementation date: 2010-05-01
Issued by the State Administration for Market Regulation
the Standardization Administration of the People's Republic of China
Contents
Foreword i
1 Scope 1
2 Normative references 1
3 Principle 2
4 Reagents 3
5 Apparatus 5
6 Sampling and sample preparation 5
7 Analytical procedures 5
8 Calculation of analysis results 10
9 Test report 12
Annex A (Informative) Precision expression 13
Annex B (Informative) Precision analysis data 14
Annex C (Normative) Flow chart of sample analytical value acceptance procedure 16
Foreword
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
Annexes A and B of this part of GB/T 6730 are informative, and Annex C is normative.
This part was proposed by China Iron and Steel Association.
This standard is under the jurisdiction of National Technical Committee on Iron Ore and Direct Reduced Iron of Standardization Administration of China.
Iron ores - Determination of total iron content - Titanium (III) chloride reduction potassium dichromate titration methods (routine methods)
Warning: Personnel using this Part of GB/T 6730 shall be familiar with normal laboratory practice. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
1 Scope
This part of GB/T 6730 specifies the method for the determination of total iron content by the titanium (III) chloride reduction potassium dichromate titration methods (routine methods).
This part is applicable to the determination of total iron content in natural iron ore, iron ore concentrate and lump ore, including iron ore sinter and pellet. Determination range (mass fraction): 25% ~ 72%.
2 Normative references
The following documents contain provisions which, through reference in this part of GB/T 6730, constitute provisions of this part. For dated references, subsequent amendments (excluding corrections) to, or revisions of, any of these publications do not apply to this part. However, parties to agreements based on this part are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.
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 6379.2-2004, ISO 5725-2:1994, IDT)
GB/T 6682 Water for analytical laboratory use - Specification and test methods (GB/T 6682-2008, ISO 3696: 1987, MOD)
GB/T 6730.1 Iron ores - Preparation of predried test samples for chemical analysis (GB/T 6730.1-1986, ISO 7764:1998, IDT)
GB/T 10322.1 Iron ores - Sampling and sample preparation procedures (GB/T 10322.1-2000, IDT ISO 3082:1998)
GB/T 12805 Laboratory glassware - Burettes (GB/T 12805-1991, ISO 385:1984, NEQ)
GB/T 12806 Laboratory glassware - One-mark volumetric flasks (GB/T 12806-1991, ISO 1042:1983, NEQ)
GB/T 12808 Laboratory glassware - One-mark pipettes (GB/T 12808-1991, ISO 648:1977, NEQ)
3 Principle
Depending on the nature of the sample and the content of coexisting elements, the sample is decomposed by any of the following methods:
a) Hydrochloric acid-sodium fluoride decomposition method: the sample is heated and decomposed by hydrochloric acid-sodium fluoride;
b) Sulfuric acid-phosphoric acid decomposition method: the sample is heated and decomposed by sulfuric acid and phosphoric acid;
c) Melting sodium carbonate-boric acid mixed flux, hydrochloric acid decomposition method: the sample is melted with sodium carbonate-boric acid mixed flux (full flux), and the frit is heated and decomposed with hydrochloric acid;
d) Melting sodium carbonate-sodium peroxide mixed flux, hydrochloric acid decomposition method: the sample is melted with sodium carbonate-sodium peroxide mixed flux, and the frit is heated and decomposed with hydrochloric acid;
e) Sintering with a mixed flux of sodium carbonate, potassium nitrate and oxalic acid, hydrochloric acid decomposition method: the sample is sintered with a mixed flux of sodium carbonate, potassium nitrate and oxalic acid at high temperature, and the sinter lump is decomposed with hydrochloric acid and sodium fluoride.
After the sample is decomposed, stannous chloride is used for reducing most of the ferric iron in the test solution, and then sodium tungstate is used as an indicator. Titanium trichloride is used for reducing all the remaining ferric iron to divalent to generate "tungsten blue". The excess reducing agent is oxidized by dilute potassium dichromate solution (or naturally oxidized by oxygen in the air). In sulfuric acid-phosphoric acid medium, with sodium diphenylamine sulfonate as indicator, ferrous iron is titrated with potassium dichromate standard titration solution, and the mass fraction of total iron is calculated.
If the copper content is greater than 0.5%, the sample is decomposed by any method capable of completely decomposing the sample, and then the iron precipitated in ammonia water is separated from the copper to perform the determination of iron.
If the content of vanadium is greater than 0.1%, the sample is melted with sodium carbonate-sodium peroxide mixed flux, and the iron is separated from the vanadium after water leaching for the determination of iron.
4 Reagents
Warning: Sodium peroxide is strongly oxidizing and cannot come into contact with reducing substances such as organics, otherwise it is liable to burn and explode. The waste of sodium peroxide shall not be wrapped in paper or similar combustible materials and then thrown into the waste box. It shall be washed with water and discharged into the sewer to avoid spontaneous combustion and fire.
Unless otherwise stated, only recognized analytically pure reagents and distilled water or laboratory water of comparable purity in accordance with GB/T 6682 shall be used.
4.1 Anhydrous sodium carbonate.
4.2 Sodium peroxide.
4.3 Magnesium oxide, previously ignited at 900°C for 1 h.
4.4 Sodium fluoride.
4.5 Sodium carbonate-boric acid mixed flux.
Take 2 portions of anhydrous sodium carbonate and 1 portion of boric acid finely ground and mixed.
4.6 Sodium carbonate, potassium nitrate and oxalic acid mixed flux.
Grind 100 g of anhydrous sodium carbonate, 7.5 g of potassium nitrate and 40 g of oxalic acid and mix well.
4.7 Hydrochloric acid, ρ is about 1.19 g/mL.
4.8 Hydrochloric acid, 1+1.
4.9 Hydrochloric acid, 1+4.
4.10 Hydrochloric acid, 1+99.
4.11 Sulfuric-phosphoric acid mixed acid, 3+3+4.
4.12 Nitric acid, ρ is about 1.42 g/mL.
4.13 Hydrogen peroxide, ρ is about 1.05 g/mL.
4.14 Aqueous ammonia, 1+1.
4.15 Aqueous ammonia, 5+95.
4.16 Sodium hydroxide solution, 10 g/L.
4.17 Sodium fluoride solution (50 g/L): stored in a plastic bottle.
4.18 Stannous chloride solution, 60 g/L.
Dissolve 6 g of stannous chloride in 20 mL of hot concentrated hydrochloric acid, dilute to 100 mL with water, mix well, and add several tin granules.
4.19 Sodium tungstate solution, 250 g/L.
Weigh 25 g of sodium tungstate and dissolve it in proper amount of water, add 5 mL of phosphoric acid and dilute to 100 mL with water.
4.20 Titanium trichloride solution, 1+14.
Take 2 mL of titanium trichloride solution (approximately 15% concentration by mass volume) and dilute to 30 mL with hydrochloric acid (1+5).
4.21 Copper sulfate, 5 g/L.
4.22 Potassium dichromate solution, 1 g/L.
4.23 Potassium permanganate solution: 4 g/L.
4.24 Sodium diphenylamine sulfonate indicator solution, 2 g/L.
4.25 Ammonium ferrous sulfate solution, c(Fe2+) = 0.050 mol/L.
Dissolve 19.7 g of ammonium ferrous sulfate [(NH4)2Fe(SO4)2·6H2O] into sulfuric acid (5+95), transferred to a 1,000 mL volumetric flask, dilute to the scale with sulfuric acid (5+95), and mix well.
Foreword i
1 Scope
2 Normative references
3 Principle
4 Reagents
5 Apparatus
6 Sampling and sample preparation
7 Analytical procedures
8 Calculation of analysis results
9 Test report
Annex A (Informative) Precision expression
Annex B (Informative) Precision analysis data
Annex C (Normative) Flow chart of sample analytical value acceptance procedure
