Direct reduced iron — Determination of metallic iron — Bromine-methanol titrimetric method

ISO 5416:2006 specifies a titrimetric method for the determination of the mass fraction of metallic iron in reduced iron ores (direct reduced iron: DRI). This method is applicable to mass fractions of metallic iron between 15 % and 95 % in DRI.

Minerais de fer préréduits — Dosage du fer métallique — Méthode titrimétrique au brome-méthanol

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Third edition

Direct reduced iron — Determination of
metallic iron — Bromine-methanol
titrimetric method
Minerais de fer préréduits — Dosage du fer métallique — Méthode
titrimétrique au brome-méthanol

Reference number
ISO 5416:2006(E)
ISO 2006

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ISO 5416:2006(E)
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©  ISO 2006
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ii © ISO 2006 – All rights reserved

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ISO 5416:2006(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Principle. 1
4 Reagents. 2
5 Apparatus . 3
6 Sampling and samples. 3
6.1 Laboratory sample. 3
6.2 Preparation of test samples. 3
7 Procedure . 3
7.1 Number of determinations . 3
7.2 Test portion . 3
7.3 Blank test and check test. 3
7.4 Determination of hygroscopic moisture content . 4
7.5 Determination. 4
8 Expression of results . 5
8.1 Calculation of mass fraction of metallic iron. 5
8.2 General treatment of results. 5
9 Test report . 7
Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test
samples. 8
Annex B (informative) Derivation of repeatability and permissible tolerance equations . 9
Annex C (informative) Precision data obtained by international analytical trials . 10
Annex D (informative) Determination of degree of metallization . 11
Annex E (informative) Decontamination of the waste solutions from the analysis . 12

© ISO 2006 – All rights reserved iii

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ISO 5416:2006(E)
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5416 was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron, Subcommittee
SC 2, Chemical analysis.
This third edition cancels and replaces the second edition (ISO 5416:1997), which has been technically
revised. It has been updated to alter the manner in which precision data are presented.

iv © ISO 2006 – All rights reserved

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Direct reduced iron — Determination of metallic iron —
Bromine-methanol titrimetric method
WARNING — This International Standard may involve hazardous materials, operations and equipment.
This International Standard does not purport to address all of the safety issues associated with its use.
It is the responsibility of the user to establish appropriate health and safety practices and determine the
applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a titrimetric method for the determination of the mass fraction of metallic
iron in reduced iron ores (direct reduced iron: DRI).
This method is applicable to mass fractions of metallic iron between 15 % and 95 % in DRI.
NOTE The term “metallic iron” means those forms of iron not bonded to oxygen or not present as pyrite.
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.
ISO 385, Laboratory glassware — Burettes
ISO 648, Laboratory glassware — One-mark pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 2596, Iron ores — Determination of hygroscopic moisture in analytical samples — Gravimetric, Karl
Fischer and mass-loss methods
ISO 2597-1, Iron ores — Determination of total iron content — Part 1: Titrimetric method after tin(II) chloride
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 10835, Direct reduced iron and hot briquetted iron — Sampling and sample preparation
3 Principle
Metallic iron is dissolved by treatment with bromine-methanol solution. The insoluble residue is separated by
filtration. The iron in the filtrate is reduced to iron(II), which is titrated with potassium dichromate solution.
NOTE Other metallic elements, such as chromium, cobalt, manganese, nickel and vanadium, are also dissolved by
the bromine-methanol solution but, except for vanadium, they do not interfere with the titration procedure.
© ISO 2006 – All rights reserved 1

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ISO 5416:2006(E)
4 Reagents
During the analysis, use only reagents of recognized analytical grade and only water that complies with
grade 2 of ISO 3696.
4.1 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml.
4.2 Sulfuric acid, ρ 1,84 g/ml, diluted 1 + 1.
4.3 Methanol, Karl Fischer reagent grade, max. 0,1 % H O.
4.4 Bromine-methanol solution, 50 ml/l.
Dissolve 5 ml of bromine in 95 ml of methanol (4.3). This solution shall be freshly prepared and used
WARNING — The preparation of the bromine-methanol solution, and all stages of the procedure where
bromine is present, shall be carried out in an efficient fume cupboard.
4.5 Hydrogen peroxide solution, 30 % (V/V).
4.6 Tin(II) chloride solution, 100 g/l.
Dissolve 119 g of tin(II) chloride dihydrate (SnC1 ·2H O), successively in small amounts, with 200 ml of
2 2
hydrochloric acid (4.1) by warming. Cool, dilute to 1 litre and mix. Add 2 g of coarsely granulated tin and store
the solution in a brown bottle.
4.7 Mercury(II) chloride solution, 50 g/l.
Dissolve 50 g of mercury(II) chloride (HgCl ) in 800 ml of hot water. Cool, dilute to 1 litre and mix.
4.8 Sulfuric acid/phosphoric acid mixture.
Add cautiously, while stirring, 150 ml of sulfuric acid (ρ 1,84 g/ml) and 150 ml of phosphoric acid (ρ 1,7 g/ml)
to 600 ml of water. Cool, dilute to 1 litre and mix.
4.9 Iron standard solution.
Dissolve 0,800 g of high purity iron(III) oxide (Fe O > 99 %) in 40 ml of hydrochloric acid (4.1). Dilute to
2 3
1 000 ml and mix.
1 ml of this solution contains 0,558 mg of iron.
If the purity of the iron(III) oxide is unknown, the solution should be standardized using a 100 ml aliquot
evaporated to a low volume.
4.10 Potassium dichromate, standard volumetric solution, c(K Cr O ) = 0,016 67 mol/l.
2 2 7
Pulverize about 6 g of potassium dichromate in an agate mortar, dry at 140 °C to 150 °C for 2 h, then cool to
room temperature in a desiccator.
Weigh 4,903 g of the dried material, dissolve in water and transfer to a 1 000 ml volumetric flask. Dilute to
volume with water and mix.
4.11 Sodium diphenylamine sulfonate, 2 g/l solution.
Dissolve 0,2 g of sodium diphenylamine sulfonate (C H NHC H SO Na) in 100 ml of water. Store the solution
6 5 6 4 3
in a brown glass bottle.
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ISO 5416:2006(E)
5 Apparatus
Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the
specifications of ISO 648 and ISO 1042 respectively, and the following
5.1 Burette, complying with the specifications of ISO 385.
5.2 Conical flask, of capacity 100 ml, diameter 50 mm to 60 mm, without concave base, for dissolving the
sample. A watch-glass or reflux condenser is required if working outside a fume cupboard.
−1 −1
5.3 Magnetic stirrer (rotational frequency 200 min to 400 min ), magnetic stirring bar without pivot ring,
polytetrafluoroethylene (PTFE) coated; diameter 5 mm, length 40 mm.
5.4 Filtering apparatus, with glass-fibre filters or plastics micro-filters , in either case with a pore size of
less than 1 µm.
6 Sampling and samples
6.1 Laboratory sample
For analysis, use a laboratory sample of minus 160 µm particle size which has been taken and prepared in
accordance with ISO 10835.
6.2 Preparation of test samples
Thoroughly mix the laboratory sample using non-magnetic materials. Taking multiple increments with a
non-magnetic spatula, extract a test sample of not less than 25 g in such a manner that it is representative of
the whole contents of the container. Prepare an air-equilibrated test sample in accordance with ISO 2596.
7 Procedure
7.1 Number of determinations
Carry out the analysis at least in duplicate in accordance with Annex A, independently, on one air-equilibrated
test sample.
NOTE The expression “independently” means that the second and any subsequent result is not affected by the
previous result(s). For this particular analytical method, this condition implies that the repetition of the procedure is carried
out either by the same operator at a different time, or by a different operator including, in either case, appropriate
7.2 Test portion
Taking several increments using a non-magnetic spatula, weigh, to the nearest 0,000 2 g, approximately
0,50 g of the air-equilibrated test sample (6.2).
7.3 Blank test and check test
In each run, one blank test and one analysis of a certified reference material of the same type of DRI shall be
carried out in parallel with the analysis of the sample(s) under the same conditions. A test sample of

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