ISO 4298:2022

INTERNATIONAL ISO
STANDARD 4298
Third edition
2022-06
Manganese ores and concentrates —
Determination of manganese content
— Potentiometric method
Minerais et concentrés de manganèse — Dosage du manganèse —
Méthode potentiométrique
Reference number
© ISO 2022
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 4
7 Sampling . 4
8 Procedure .4
8.1 Test portion . 4
8.2 Blank test . 4
8.3 Determination of hygroscopic moisture content . 4
8.4 Decomposition of test portion . 5
8.5 Treatment of residue . 5
8.6 Titration. 5
9 Expression of results . 5
9.1 Calculation of manganese content . 5
9.2 General treatment of results . 6
9.2.1 Expression of precision . 6
9.2.2 Determination of analytical result . 7
9.2.3 Between-laboratories precision . 7
9.2.4 Check for trueness . 7
9.2.5 Calculation of final result . 8
10 Test report . 8
Annex A (informative) Additional information on the international interlaboratory test .9
Annex B (normative) Flow chart for the acceptance procedure of test results .11
Bibliography .12
iii
Foreword
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 132, Ferroalloys.
This third edition cancels and replaces the second edition (ISO 4298:1984), which has been technically
revised.
The main changes are as follows:
— in Clause 4, the description of reaction has been reworded to better explain the method;
— in 5.12 (previously in 5.10), the detailed specification of “electrolytic manganese” has been added
and described as “electrolytic manganese metal flakes”;
— in 5.13 (previously in 5.11), the commercially available standard solution has been added as an
alternative, and variations in concentration shall be taken into account for the calculation of the
results in 9.1;
— in 5.14 (previously 5.11.1), the amount of aliquot portion of the manganese standard reference
solution and the saturated sodium pyrophosphate solution has been reduced, and the specification
of the beaker has been changed;
— in 5.15 (previously 5.11.2), the amount of aliquot portion of the potassium permanganate solution
and the saturated sodium pyrophosphate solution has been reduced, and the specification of the
beaker has been changed;
— in Clause 6, the description of pH meter has been replaced with a list of potentiometric titration
apparatus in line with the current status of the development of the instrument, including the
apparatus for potentiometric titration in 6.1, pH determination in 6.2 and titration assembly in 6.3;
— in Clause 8, a new paragraph of the definition of test portion has been added in 8.1 and the amount
of test portion in 8.1 (previously 8.2) has been reduced from 1,0 g to 0,50 g;
— in Clause 8, a new paragraph of the definition and requirement of determination of hygroscopic
moisture content has been added in 8.3;
iv
— in 8.4 (previously 8.2), the amount of acids has been reduced, the times of washing have been
changed, and the detailed usage of watch-glass and the provision of filter volume have been added;
— in 8.6 (previously 8.4), the amount of aliquot portion of the solution and the saturated sodium
pyrophosphate solution has been reduced, and the specification of one-mark volumetric flask and
the beaker have been changed;
— in 9.1, the formula of the manganese content has been replaced with three new calculating formulae
which take into account the hygroscopic moisture content of the test portion;
— in 9.2, the paragraph of the “permissible tolerances on results” has been replaced with the “general
treatment of results”;
— Clause 10, the test report has been added;
— Annex A, “Additional information on the international interlaboratory test” has been added;
— Annex B, “Flow sheet of the procedure for the acceptance of teat results” has been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
INTERNATIONAL STANDARD ISO 4298:2022(E)
Manganese ores and concentrates — Determination of
manganese content — Potentiometric method
1 Scope
This document specifies a potentiometric method for the determination of the manganese content of
manganese ores and concentrates with manganese content equal to or greater than a mass fraction of
15 %.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 310, Manganese ores and concentrates — Determination of hygroscopic moisture content in analytical
samples — Gravimetric method
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 4296-1, Manganese ores — Sampling — Part 1: Increment sampling
ISO 4296-2, Manganese ores — Sampling — Part 2: Preparation of samples
ISO 80000-1:2009, Quantities and units — Part 1: General
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
The method is based on the titration of manganous ion with permanganate ion in neutral pyrophosphate
solution, the manganese(II) being oxidized, the permanganate ion reduced, to a pyrophosphate complex
2+ −
of the +3 state (the stoichiometry ratio of Mn to MnO is 4:1).
Decomposition of a test portion by treatment with hydrochloric acid, nitric, perchloric and hydrofluoric
acids. Separation of insoluble residue, and reservation of the filtrate as the main solution. Ignition of
the residue, fusion with sodium carbonate, leaching of the melt with hydrochloric acid and combination
with the main solution. Addition of an aliquot portion of the resulting solution to sodium pyrophosphate
solution, adjustment of the pH to 7,0, and potentiometric titration with potassium permanganate
standard volumetric solution.
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only
grade 3 water as specified in ISO 3696.
5.1 Sodium carbonate (Na CO ), anhydrous.
2 3
5.2 Hydrochloric acid, ρ = 1,19 g/ml.
5.3 Hydrofluoric acid, ρ = 1,14 g/ml.
5.4 Perchloric acid, ρ = 1,51 g/ml.
5.5 Nitric acid, ρ = 1,40 g/ml.
5.6 Potassium permanganate, degree of purity not less than 99,5 %.
5.7 Sodium carbonate, 50 g/l solution.
5.8 Hydrochloric acid, diluted 1 + 4.
5.9 Saturated sodium pyrophosphate solution. Dissolve 120 g of sodium pyrophosphate
decahydrate (Na P O ·10H O) with 1 000 ml of water. After 24 h, the supernatant is obtained for use.
4 2 7 2
5.10 Potassium-permanganate (KMnO ), recrystallized. Dissolve 250 g of potassium permanganate
(5.6) with 800 ml of hot water (90 °C) in a 1 000 ml beaker. Filter the solution under vacuum through a
filter crucible with a sintered glass plate No.3 (6.5). Cool the filtered solution in an ice bath to 10 °C, while
stirring vigorously. Allow the fine-grained precipitate to settle. Then pour out the solution, transfer the
crystalline mass to the crucible with sintered glass plate No.3 (6.5) and place under suction. Repeat the
recrystallization.
After thorough suction, transfer the crystalline mass thus obtained to a glass or porcelain dish and
dry in air in the dark, protecting from dust. When the crystalline mass no longer sticks together when
crushed with a glass rod, dry it at 80 °C to 100 °C for 2 h to 3 h in a drying oven. Then transfer it to a
stoppered brown glass bottle.
Potassium permanganate thus obtained contains 34,76 % (mass fraction) of manganese and is non-
hygroscopic.
5.11 Bromothymol blue indicator, 0,4 g/l solution.
5.12 Manganese, standard reference solution, corresponding to 1 g of Mn per litre. Place 10,00 g of
electrolytic manganese metal flakes (purity not less than 99,95 %) in a 400 ml or 500 ml beaker. Add a
mixture of 50 ml of water and 5 ml of the nitric acid (5.5) and leave for a few minutes until the surface
becomes bright. Wash the treated manganese six times with water, then with acetone, and dry at 100 °C
for 10 min.
Place 1,00 g of the treated electrolytic manganese in a 400 ml or 500 ml beaker, and add 20 ml of sulfuric
acid (ρ = 1,84 g/ ml, diluted 1 + 1) and about 100 ml of water. Boil the solution for a few minutes, cool,
transfer to a 1 000 ml one-mark volumetric flask, dilute to the mark with water and mix.
1 ml of this standard solution contains 1 mg of Mn.
5.13 Potassium permanganate, standard volumetric solution, c (1/5 KMnO ) ≈ 0,1 mol/l. Dissolve
3,20 g of potassium permanganate (5.6) in 1 000 ml of water, allow to stand for six days, then transfer
to a brown glass bottle and mix.
Alternatively, commercially available standard solutions of known concentration can be used instead of
standard solutions produced in the laboratory. Variations in concentration shall be taken into account
for the calculation of the results.
5.14 Standardization with the manganese standard reference solution (5.12).
Transfer 50,00 ml of the manganese standard reference solution (5.12) into a 400 ml beaker and
add, while stirring, 150 ml of the saturated sodium pyrophosphate solution (5.9). Adjust the pH of
the solution to 7,0 with hydrochloric acid (5.8) [check the pH using either the pH electrode (6.2) or
the bromothymol blue indicator (5.11)] and titrate with the potassium permanganate solution (5.13)
using the potentiometric titration apparatus (6.1, 6.2, 6.3) until the maximum peak deflection on the
voltmeter is observed.
Carry out a blank test, omitting the standard manganese solution.
The mass concentration of the potassium permanganate solution, ρ , is given by Formula (1):
m
ρ = (1)
VV−
where
m is the mass, in grams, of manganese present in the aliquot portion of the manganese
stand
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