ISO 157:2025
(Main)Coal — Determination of forms of sulfur
Coal — Determination of forms of sulfur
This document specifies methods of determining the sulfate and pyritic sulfur mass fraction of coals, and of calculating the amount of organic sulfur present.
Charbon — Détermination de la teneur en différentes formes de soufre
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Standards Content (Sample)
International
Standard
ISO 157
Third edition
Coal — Determination of forms
2025-05
of sulfur
Charbon — Détermination de la teneur en différentes formes
de soufre
Reference number
© ISO 2025
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Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Preparation of test sample . 1
6 Separation of sulfate and pyritic sulfur . 3
6.1 Principle .3
6.2 Reagents .3
6.3 Apparatus .3
6.4 Procedure .4
6.4.1 Test portion .4
6.4.2 Extraction .4
7 Determination of sulfate sulfur . 5
7.1 Principle .5
7.2 Reagents .5
7.3 Apparatus .5
7.4 Procedure .6
7.5 Blank test .7
7.6 Expression of results .7
7.7 Precision . . .7
7.7.1 Repeatability limit .7
7.7.2 Reproducibility limit .7
8 Determination of pyritic sulfur . 7
8.1 Principle .7
8.2 Reagents .8
8.2.1 Titrimetric, colorimetric and atomic absorption spectrometric finishes .8
8.2.2 Titrimetric finish only .8
8.2.3 Colorimetric and atomic absorption spectrometric finishes .9
8.2.4 Colorimetric finish only .9
8.2.5 Atomic absorption spectrometric finish only .9
8.3 Apparatus .9
8.4 Procedure .9
8.4.1 Preparation of test solution .9
8.4.2 Titrimetric finish .10
8.4.3 Colorimetric finish .10
8.4.4 Atomic absorption spectrometric finish .11
8.5 Blank test . 12
8.6 Expression of results . . 12
8.6.1 Titrimetric finish . 12
8.6.2 Colorimetric finish . 13
8.6.3 Atomic absorption spectrometric finish . 13
8.7 Precision . . .14
8.7.1 Repeatability limit .14
8.7.2 Reproducibility limit .14
9 Determination of organic sulfur . 14
9.1 Principle .14
9.2 Calculation .14
10 Calculation to other bases. 14
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11 Test report . 14
Annex A (informative) Derivation of factors used in the calculations .16
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Foreword
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This document was prepared by Technical Committee ISO/TC 27, Coal and coke, Subcommittee SC 5, Methods
of analysis.
This third edition cancels and replaces the second edition (ISO 157:1996), which has been technically
revised. It also incorporates the Technical Corrigendum ISO 157:1996/Cor. 1:1999.
The main changes are as follows:
— Clause 2 has been updated;
— Clause 3 has been added and subsequent clauses have been renumbered;
— Formula (5), for organic sulfur, has been added;
— the test report has been updated.
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.
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