ISO 5068-1:2025

International
Standard
ISO 5068-1
Second edition
Brown coals and lignites —
2025-05
Determination of moisture —
Part 1:
Indirect gravimetric method for
total moisture
Charbons bruns et lignites — Détermination de l'humidité —
Partie 1: Méthode gravimétrique indirecte pour l'humidité totale
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Single-stage method .1
4.2 Two-stage method .1
5 Reagent . 2
6 Apparatus . 2
7 Sample . 4
7.1 General .4
7.2 Single-stage method .4
7.3 Two-stage method .4
8 Procedure . 5
8.1 Single-stage method .5
8.2 Two stage method .5
8.2.1 Air dry loss moisture .5
8.2.2 Residual moisture .5
9 Expression of results . 6
9.1 Single-stage method — Total moisture .6
9.2 Two-stage method .6
9.2.1 Air dry loss moisture .6
9.2.2 Residual moisture .6
9.2.3 Total moisture .7
10 Precision of method . 7
10.1 Repeatability .7
10.2 Reproducibility critical difference .7
11 Test report . 7
Annex A (informative) Nitrogen-purification train . 8

iii
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 second edition cancels and replaces the first edition (ISO 5068-1:2007), which has been technically
revised.
The main changes are as follows:
— referenced documents have been updated;
— terms and definitions have been updated;
— the test report has been updated.
A list of all parts in the ISO 5068 series can be found on the ISO website.
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.

iv
International Standard ISO 5068-1:2025(en)
Brown coals and lignites — Determination of moisture —
Part 1:
Indirect gravimetric method for total moisture
1 Scope
This document specifies two methods for determination of the total moisture of brown coals and lignites
using an indirect gravimetric single-stage method and a two-stage method.
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 1213-2, Coal and coke — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 13909-4, Coal and coke — Mechanical sampling — Part 4: Preparation of test samples of coal
ISO 18283, Coal and coke — Manual sampling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1213-2 apply.
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
4.1 Single-stage method
A sample, prepared using a closed mill, is dried to a constant mass at a temperature of 105 °C to 110 °C in an
atmosphere of nitrogen. The total moisture mass fraction is calculated from the loss in mass of the sample.
4.2 Two-stage method
At the first stage, the coarsely ground sample is dried either at ambient temperature or at a higher
temperature not exceeding 40 °C, to reach equilibrium with the surrounding atmosphere. At the second
stage, the sample dried in an air atmosphere (air-dry sample) is crushed and dried to a constant mass at
a temperature of 105 °C to 110 °C in an atmosphere of nitrogen. The total moisture is calculated from the
losses in mass during the two drying stages.

5 Reagent
5.1 Desiccant, fresh or freshly regenerated and pr
...