ISO 20336:2017

INTERNATIONAL ISO
STANDARD 20336
First edition
2017-10
Solid mineral fuels — Determination
of total sulfur by Coulomb titration
method
Combustibles minéraux solides — Détermination de la teneur totale
en soufre par la méthode de titrage de Coulomb
Reference number
ISO 20336:2017(E)
©
ISO 2017

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ISO 20336:2017(E)

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ISO 20336:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagent and materials . 1
6 Apparatus . 2
7 Preparation of test sample . 3
8 Procedure. 4
8.1 Preparation of test . 4
8.2 Calibration . 4
8.3 Calibration procedure . 4
8.4 Procedure . 5
8.5 Calibration check . 5
9 Expression of result . 6
10 Precision . 6
10.1 Repeatability limit . 6
10.2 Reproducibility limit . 6
11 Test report . 6
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ISO 20336:2017(E)

Foreword
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This document was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee
SC 5, Methods of analysis.
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ISO 20336:2017(E)

Introduction
The objective of this document is to provide an alternative method for determining the total sulfur
content in solid mineral fuels with high-temperature combustion — Coulomb titration using automated
instruments.
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INTERNATIONAL STANDARD ISO 20336:2017(E)
Solid mineral fuels — Determination of total sulfur by
Coulomb titration method
1 Scope
This document specifies an alternative method of determining the total sulfur content of coal and coke
by high-temperature combustion — Coulomb titration.
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 687, Solid mineral fuels — Coke — Determination of moisture in the general analysis test sample
ISO 5068-2, Brown coals and lignites — Determination of moisture content — Part 2: Indirect gravimetric
method for moisture in the analysis sample
ISO 11722, Solid mineral fuels — Hard coal — Determination of moisture in the general analysis test
sample by drying in nitrogen
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
4 Principle
In the presence of the catalyst, a weighed sample is combusted at 1 150 °C in a stream of purified air.
The sulfur oxides are formed and dissolved in the electrolytic solution. The sulfur dioxides are titrated
by the iodine and bromine librated from the electrolysis of the potassium iodide and potassium
bromide solution. The quantity of the electricity consumed by electrolysis is integrated and used to
calculate the content of sulfur dioxides. The instrument is calibrated with certified reference materials.
The percentage of total sulfur in the sample is calculated according to the sulfur dioxides content and
the prior calibration.
5 Reagent and materials
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only
distilled water or water of equivalent purity.
5.1 Potassium iodide.
5.2 Potassium bromide.
5.3 Glacial acetic acid.
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ISO 20336:2017(E)

5.4 Self-indicating silica gel, industrial grade.
5.5 Sodium hydroxide, chemical grade.
5.6 Electrolytic solution.
5 g of potassium iodide (5.1) and 5 g of potassium bromide (5.2) are dissolved in (250 to 300) ml of
water, then add 10 ml of glacial acetic acid.
5.7 Glass wool.
5.8 Aluminosilicate wool.
5.9 Catalyst, tungsten trioxide.
5.10 Certified reference materials (CRMs), coal or coke.
6 Apparatus
6.1 Instrument.
For determining sulfur by Coulomb titration, commercially available, consisting of the following
(
...